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3.5 from 72 votes
French Onion Tart cut into square slices, golden brown, and scattered with thyme sprigs.
French Onion Tart
Prep Time
30 mins
Cook Time
40 mins
Resting Time
1 hr
Total Time
1 hr 10 mins
 
A tender pastry crust topped with sweet roasted onions and just a hint of herbs make this a onion tart a party favorite.

Course: Appetizer
Cuisine: French
Keyword: french onion tart, onion tart
Servings: 8 servings
Calories: 345 kcal
Ingredients
Pastry
  • 2 cups all purpose flour
  • 1/2 tsp kosher salt
  • 1 Tbsp sugar
  • 12 Tbsp cold unsalted butter, diced (1 1/2 sticks)
  • 1/2 cup ice water
Onion Topping
  • 1 cup gruyere cheese, shredded (4 oz)
  • 1 1/2 tsp fresh thyme, minced
  • 2 tsp fresh chives, minced
  • 1 1/4 lbs sweet onions, (about 3 medium onions)
  • 1 Tbsp heavy cream
  • 3 Tbsp unsalted butter, diced
  • 1 tsp kosher salt
Instructions
Pastry
  1. Place the flour, salt, and sugar in the bowl of a food processor fitted with the steel blade. Pulse for a few seconds to combine.

  2. Add the butter and pulse 10 to 12 times, until the butter is in small bits the size of peas.
  3. With the motor running, pour the ice water down the feed tube and pulse just until the dough starts to come together. Dump onto a floured board and knead quickly into a ball. Wrap in plastic and refrigerate for at least 1 hour.
Prepare the tart
  1. Preheat the oven to 400 degrees and line a sheet pan with parchment paper.

  2. Roll the dough between two sheets of lightly floured wax paper, slightly larger than 10 x 14 inches. Using a ruler and a small knife, trim the edges. Place the dough on the prepared sheet pan and refrigerate while you prepare the onions.
  3. Sprinkle the rolled pastry with the cheese right to the edges.
  4. Sprinkle with thyme and chives.
  5. Peel, halve, and very thinly slice the onions into half moons, keeping the moons intact. Place the onion half moons on the pastry in diagonal lines, just barely overlapping and brush lightly with cream.

  6. Dot with the butter and sprinkle with salt.
  7. Bake for 40 mins or until the tart is golden and browned. Cover the edges with foil if the tart is getting too brown during baking.
  8. Let cool slightly and cut into squares to serve. Serve warm or at room temperature.
Recipe Notes
  • The dough comes together in minutes in your food processor and can be made well in advance and frozen until you're ready to use it.
  • There's no pre-cooking of the onions on the stove like many onion tarts require. They're simply sliced thin and arranged over a sprinkling of grated cheese and herbs and baked until golden brown and caramelized.
  • The tart can be sliced into squares, strips, or wedges, but no matter how you slice it (yes I went there), it's just plain delicious.
  • Tart can be served right out of the oven or at room temperature, which makes it ideal for parties.

*Adapted from The Barefoot Constessa's French Apple Tart

Nutrition Facts
French Onion Tart
Amount Per Serving
Calories 345 Calories from Fat 198
% Daily Value*
Fat 22g34%
Saturated Fat 14g88%
Cholesterol 59mg20%
Sodium 443mg19%
Potassium 142mg4%
Carbohydrates 32g11%
Fiber 2g8%
Sugar 4g4%
Protein 4g8%
Vitamin A 710IU14%
Vitamin C 5.6mg7%
Calcium 27mg3%
Iron 1.6mg9%
* Percent Daily Values are based on a 2000 calorie diet.