Golden Onion Tart with Gruyère and Thyme

Golden Onion Tart with Gruyère and Thyme

This tart is a vehicle for caramelized onions. It’s also inspired by an appetizer I ate years ago in a Swiss auberge overlooking the Lake of Geneva. It’s been so long, I can’t remember the name of the restaurant, but I do remember the onion tart. It was simple and rustic, just like the half-timbered dining room with its roaring open fire where we tasted it. Sweet, rich and minimal, this tart was perfection in its simplicity. Today I make a version of this memory while we enjoy another view from our California home. I like to serve it in small slivers with glass of wine before dinner.

Golden Onion Tart with Gruyère and Thyme
Serves 8 to 12

For the dough – adapted from a recipe by Alice Waters:
1 cup all-purpose flour
1/2 teaspoon salt
6 tablespoons unsalted butter, chilled, cut in 1/4 inch cubes
3 tablespoons ice water

Stir flour and salt together with a fork. Toss in butter. Work the butter into the flour with a fork or your fingertips until it resembles coarse meal, with some pieces of the butter apparent. Sprinkle in the water while stirring with a fork until the dough comes together, adding another tablespoon of water if necessary. Form into a ball and flatten. Wrap in plastic wrap and refrigerate 1 hour

For the filling:
2 tablespoons olive oil
2 pounds yellow onion, peeled and thinly sliced
1 teaspoon salt
2 tablespoons port wine
1 teaspoon freshly ground black pepper
2 ounces finely grated Gruyère cheese
1 teaspoon fresh thyme, plus extra for garnish
1 egg, slightly beaten

Heat olive oil over medium heat in a deep skillet or pot. Add onions and salt. Cook onions, stirring occasionally, until they are golden brown, soft and squidgy, about 30 minutes. Add port wine and cook, stirring, 2 minutes. Remove onions from heat and stir in the pepper. Cool slightly.
While the onions are cooling, roll out the dough to fit in the bottom and up the side of a 10 inch round tart tin. Sprinkle half of the cheese over the bottom of the tart. Spoon onions into the shell and spread evenly. Sprinkle 1 teaspoon thyme over the onions. Brush the exposed crust rim with the egg wash. Sprinkle the tart and crust with the remaining cheese.
Bake in a preheated 375 F. oven until the crust is firm and golden and the onions have turned a rich golden brown, without blackening, about 30 minutes. Remove and cool slightly. Serve slightly warm or at room temperature garnished with thyme sprigs.