For the past few months, my ideas and inspiration for making new meals gravitated towards baking. Either sweet or savory, it did not matter as long as my hands are touching dough or mixing batter. My excuse is the winter weather and the need to feel warmth even if it comes from a 350-degree oven. But the truth is I love to bake. I can’t lay it all on the winter chill. Whether it is savory, like my beef empanadas, or something sweet like lemon syrup saffron cake, I get immense satisfaction stirring, whipping, kneading and baking. Now, all I want to do is bake bread and make this irresistible onion tart.
For the past month or so, I put this savory tart on the back burner. Actually, I waffled between making French onion soup, a classic French flatbread Pissialadière, and a creamy onion tart. Every time I saw a photo of caramelized onions topping a savory crust or custard on social media my hunger resurfaced. Clearly, I craved the taste of slowly browned and fragrant onions. It was time to give in.
I have Mom’s recipe for Quiche Loraine that I have made for years, but I wanted to try something a little different. With the premise of testing a new recipe from Deborah Madison’s cookbook, Vegetable Literacy, I forged ahead. It is a big tease looking through a vegetable cookbook in the middle of February. All these tantalizing photos of bright spring and summer vegetables dancing off the pages as I look out my window and feel the chill of the snow-covered landscape. Yet, in between my daydreams of freshly harvested greens and succulent sweet tomatoes, I kept returning to the chapter on onions and this fragrant onion tart made quite an impression.
Pastry Crust for an Onion Tart
There were two things that caught my attention, the first one being she makes a 100% whole wheat pastry crust. Often, I add some whole wheat pastry flour to my flour mix when I make pie dough. It adds a nutty flavor and more texture. It is my experience, a pie crust made with nothing but whole wheat flour is often dry and heavy. In all my years of testing Deborah Madison’s recipes, I never experienced a heavy or dry recipe. Her cooking is not the vegetarian cooking of the 70’s, it is much more refined. Though I am sure her whole wheat pie crust is a good one, I did change the recipe slightly by substituting some whole wheat pastry flour with the whole wheat flour. There is less gluten in pastry flour, so I knew it would help create a lighter crust.
Fillings in Onion Tart
Additionally, I was surprised that she uses white onions in the tart not sweet onions like Vidalia onions. The only times I see white onions in a recipe is for Mexican food. White onions are less sharp than yellow onions, therefore your eyes will not sting as much when you mince them. That makes a big difference when you must dice 3 large onions. A good sharp knife helps as well because it makes a cleaner cut.
The onions are diced and cooked in butter until light brown. This process takes some time but be patient. It won’t take as long as caramelizing onions. The subtle difference between browned and caramelized onions is noticeable here with a light onion flavor that is delightfully sweet. I love caramelized onions, but I have never tasted onions so sweet before. Also, the sweet browned onions are very fragrant which compliments the onion tart nicely.
Instead of bacon, I quickly fried sliced prosciutto and added it to the filling. The smokiness of bacon tastes great with cheese and eggs, but I wanted to keep the flavor on the delicate side to compliment the sweet onion flavor of the tart. If you ever have more prosciutto than you need, this is the perfect recipe to help use up a couple of slices.
Onion Tart for Days
After making this onion tart I still crave that luscious sweetness and fragrance of slowly cooked browned onions. It is just too good to eat once in a while. Fragrant, sweet, and irresistible onion tart is perfect for a light supper, luncheon, brunch or appetizer. Additionally, it is a great choice for cocktail party food when portioned into small bites. This is a meal for any season or any time of day and a real crowd pleaser.
Irresistible Onion Tart
Fragrant and sweet browned onions are the foundation of this savory custard tart. It may have rich ingredients, but it won't make you feel heavy. I love how aged or smoked Gouda adds some extra depth of flavor to the tart, but Gruyère or Comte are good substitutes. If you do not have whole wheat pastry flour you can use all whole wheat flour instead. You can make the pastry dough and cook the onions a day ahead. The pastry dough will keep in the refrigerator covered in plastic wrap for 3 days. Or, freeze it for up to 3 months. The onions are best eaten within 24 hours of making them. Onion tart is perfect for brunch, lunch, a light supper or as an appetizer for a cocktail party. It is a very versatile food you can make all year long. Special equipment: 9-inch (23 cm) tart pan with removable bottom. You can use any shape, square, circle or an 11 x 8.5-inch ( 28.5 x 20 cm) rectangle tart pan. Stand mixer (optional) Rimmed sheet pan large enough to hold your tart pan. This recipe is slightly adapted from Vegetable Literacy by Deborah Madison.
- ¾ cup plus 2 Tb (123 g) Whole wheat flour
- ¼ cup (38 g) whole wheat pastry flour
- 6 TB (106 g) cold butter, cut into small pieces
- ½ tsp Kosher salt
- 3 TB ice water
Onion Tart filling
- 1 TB olive oil for frying the prosciutto
- 2 thin slices of prosciutto or 2 pieces of bacon (optional)
- 2 TB (7 g) butter
- 1½ lbs (725 g) white onions, diced
- 2 tsp fresh thyme or rosemary minced
- Kosher salt
- Freshly ground black pepper
- 3 eggs
- ½ cup (125 ml) milk
- ½ cup (125 ml) crème fraîche or heavy cream
- 1 cup (70 g) aged or smoked Gouda cheese, grated using the large holes on a box grater
Make the pie dough
Make the dough by hand or use a stand mixer.
By hand: Add the two types of flour and Kosher salt to a large bowl. Add the butter and mix the butter and flour with your hands. Press down on the butter between your thumbs and fingers to break up the pieces and press into the flour. Continue to do this until the butter and flour are mixed together and looks like pebbles.
Add the water and mix together with your hands. Add more water if it looks and feels dry, about a teaspoon at a time.
Gather the dough and turn it out onto the counter. Press together and form a flat disc in the shape of your tart pan, about an inch (2.5 cm) thick. A circle, square or rectangle shape.
Wrap in plastic wrap and refrigerate for one hour or more. The tart dough can be made 3 days in advance and kept wrapped in the refrigerator.
By stand mixer: Add the flour to the bowl of a stand mixer. Add the pieces of butter and mix the butter and flour on low until the flour looks like pebbles. Add the water and stir on low speed until just mixed together. Add more water if the pastry dough looks dry. Be careful not to over-mix the dough. Turn the dough onto a counter and shape into a flat disc into the shape of your tart pan. Cover with plastic wrap and refrigerate for one hour or more.
Make the tart filling
Preheat the oven to 400°F / 200°C. If you have a baking stone place it in your oven on the middle rack. For a crispy bottom crust, you want to heat the stone in the oven for an hour before baking.
If using the prosciutto, add 1 tablespoon of extra virgin olive oil to a skillet and turn the heat to medium-high. Slice the prosciutto into strips, about a 1/2-inch (1 cm) wide and not longer than 2-inches (5 cm) long. When the skillet is hot, add the sliced prosciutto and cook until the strips are brown and crispy. Stir occasionally to prevent the strips from sticking and burning. About 5 minutes. Turn off the heat and spoon the prosciutto slices on a plate. Set aside.
If you are using bacon add the two pieces of bacon to a hot and dry skillet and cook the bacon until they are brown and crisp. Turn the pieces over every now and then for even browning. Remove the bacon from the pan onto a plate lined with paper towels and pat dry. When the bacon is cool, crumble them into bite-size pieces. Set aside.
Wipe out the skillet with a paper towel. Turn the heat to medium and add the butter. When the butter is melted and stops sizzling, add the diced onions. Stir to coat the onions with butter. Add the thyme, a pinch of Kosher salt and a couple of grounds of fresh black pepper. Stir to mix.
Cook the onions on medium to medium-low until they are very soft and lightly browned, not caramelized, but starting to go in that direction. This is a slow process, about 25 minutes. The onions will be very soft and translucent with an even light brown color. While cooking, occasionally stir the onions for even browning and prevent them from sticking and burning. Taste for seasoning and add more thyme, Kosher salt or black pepper if needed. Turn off the heat and cool.
Remove the tart dough from the refrigerator and let it rest on a lightly floured work surface for 10 minutes. Pound the dough with your rolling pin a few times to relax and shape the dough. Roll the dough in the shape of your tart pan to about a ¼-inch (.5 cm) thickness, and large enough to fit the shape of your tart pan with a slight overhang. For a 9-inch (23 cm) round tart pan the diameter should be around 12-inches (30 cm).
Drape the dough into your tart pan and trim the edges to an inch (2.5 cm) overhang. Fold the edge of the dough inward and press along the sides and bottom of the pastry to fit the dough into the pan. The height of the tart is equal to the height of the pan. Place the tart pan on a rimmed sheet pan and loosely cover the tart with plastic wrap. Chill the tart in the refrigerator for 15 - 20 minutes.
In a small bowl, whisk together the eggs, milk and crème fraîche.
When the onions are cool and just before you want to assemble the tart, add the grated cheese, onions, and prosciutto if using, to the egg mixture. Stir to mix.
Remove the tart from the refrigerator and add the egg mixture. Even out the filling and place in the oven. Bake until the tart is golden brown and set in the middle, about 45-50 minutes.
Remove from the oven and cool to room temperature. Remove the side of the tart pan by resting the tart on top of a large can, (like canned tomatoes), and slide the side rim down. Make sure the crust is not sticking anywhere along the rim before you slide it off.
Serve warm or room temperature.
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