Author Notes: I have a distant memory of an onion tart I was served with an apero many years ago in Switzerland. I don't remember the name of the restaurant, but I do remember the onion tart. It was all about onion: minimal and intense. Since then, I have created my own version with this tart in mind. A mountain of onion is reduced to a sweet, squidgy heap which continues to caramelize while baking in a tart shell. To temper the outrageous sweetness of the onions, I splash them with a little port wine before baking, and sprinkle the shell and the top of the tart with salty, nutty Gruyere cheese. I like to cut the tart in tiny slivers and offer it as an appetizer. - TasteFood
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. Using fingertips, work the butter into the flour until it resembles coarse meal, with some pieces of the butter apparent. Sprinkle in the water while stirring with the 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.
- This recipe was entered in the contest for Your Best Late Winter Tart (Sweet or Savory)