CARAMELIZED ONION AND GRUYERE TART

Active time: 25 minutes Total time: 2 hours Yield: 6 to 8 servings

DOUGH:

1 cup all-purpose flour ½ teaspoon salt

6 tablespoons chilled unsalted butter, cut into ¼-inch cubes

3 tablespoons ice water

FILLING:

2 tablespoons olive oil

2 pounds yellow onions, peeled and thinly sliced

1 teaspoon salt

2 tablespoons Calvados (apple brandy)

½ teaspoon freshly ground black pepper

3 ounces finely grated Gruyere cheese, divided

1 teaspoon fresh thyme, plus extra for garnish

1 egg, slightly beaten

Prepare the crust: Combine the flour and salt in a food processor and pulse once or twice to combine. Add the butter and pulse until the dough resembles coarse meal, with some pieces of the butter visible. Add the water and pulse once or twice — just until the dough comes together, adding another tablespoon of water if necessary.

Dump the dough onto a work surface and form it into a disk. Wrap in plastic and refrigerate for at least 1 hour.

Heat the oven to 375 F.

Heat the olive oil over medium in a deep skillet or pot. Add the onions and salt; cook until the onions are golden brown, soft and squidgy, 35 to 40 minutes, stirring occasionally. Add the Calvados and black pepper and cook until the liquid evaporates, 1 to 2 minutes, stirring frequently. Remove from the heat and cool while you roll out the dough.

Roll out the dough to fit in the bottom and up the sides of a 10-inch round tart tin with a removable bottom. Sprinkle half the cheese over the bottom of the tart. Spread the onions in the shell and sprinkle the thyme over the onions. Brush the exposed crust rim with the egg wash. Sprinkle the tart and crust with the remaining cheese.

Bake the tart until the crust is firm and golden and the onions are deeply colored without blackening, about 30 minutes. Remove and cool slightly. Serve slightly warm or at room temperature, garnished with additional thyme.