Sweet Onion Tart
Ingredients
&w=3840&q=75){kind=small}
&w=3840&q=75){kind=small}
&w=3840&q=75){kind=small}
&w=3840&q=75){kind=small}
- 1 1/4 cups all-purpose flour
- 1/2 tsp fine sea salt
- 8 tbsp unsalted butter – cold, cut into cubes
- 4 tbsp ice water – ice-cold
- 2 tbsp unsalted butter
- 2 pounds sweet onions – thinly sliced (~5 medium sweet onions)
- 1 tsp kosher salt
- 3 eggs – large
- 1 cup heavy cream
- 1/4 tsp ground nutmeg
- 1/4 tsp black pepper – freshly ground
- 3 ounces Gruyère cheese – coarsely grated
Instructions
1. Make the pastry: In a mixing bowl, combine the all-purpose flour and fine sea salt. Cut in the cold, cubed unsalted butter until pea-sized. Sprinkle in the ice water and mix just until the dough comes together; form into a disk, wrap, and chill 30 minutes.
2. Prepare the shell: On a lightly floured surface, roll the dough to about 12 inches. Fit into a 9-inch tart pan with a removable bottom, trim the edge, and dock the base with a fork. Chill 15 minutes while you heat the oven to 375°F (190°C).
3. Blind-bake: Line the chilled shell with parchment and fill with pie weights. Bake 15 minutes, then remove weights and parchment and bake until lightly golden, 8–10 minutes more. Set on a rack to cool slightly.
4. Cook the onions: Melt the 2 tbsp unsalted butter in a large skillet over medium-low heat. Add the sweet onions and kosher salt; cook, stirring often, until very soft and pale golden without browning, 25–30 minutes. Let cool 10 minutes.
5. Make the custard: In a bowl, whisk the eggs, heavy cream, ground nutmeg, and black pepper until smooth.
6. Assemble: Stir the cooled mixture into the custard, then spread evenly in the warm tart shell. Sprinkle the Gruyère cheese over the top.
7. Bake until the filling is set around the edges with a slight wobble in the center and the top is golden, 25–30 minutes. Cool 10–15 minutes, remove the outer ring, slice, and serve warm or at room temperature.
Sweet Onion Tart is a savory French-style tart that highlights the gentle sweetness of long-cooked onions against a crisp, buttery crust. The filling is a silky custard enriched with cream and eggs, accented by a hint of nutmeg and a restrained layer of Gruyère for depth. The texture contrast—flaky base, tender onions, and softly set custard—makes it elegant yet comforting, perfect as a starter, lunch, or light supper.
Rooted in French tart-making, this dish echoes the traditions of tarte à l’oignon popular in regions like Alsace and across eastern France. Over time, cooks have adapted it to local onions, including especially sweet varieties like Vidalia or Walla Walla, while preserving the technique of slowly sweating onions rather than deeply caramelizing them. It stands alongside quiches as a bistro classic, frequently served warm with a simple salad and a glass of crisp white wine.