A weeknight tart of caramelized onions and thick-cut Swiss cheese in a butter crust. The cheese melts into the soft onions for a supper that tastes like you spent hours but asks only for a sheet pan and one knife. Serve with a green salad.

Serves 2. 45 minutes, 15 at the stove.

About 760 calories a serving, 24 g protein, 57 g carbohydrate, 48 g fat. From USDA figures for 100% of the ingredients; amounts are the recipe's.

Cook mode

1. Rub 4 tablespoons butter into 1 cup flour with 1/4 teaspoon salt until it looks like breadcrumbs, then add cold water a tablespoon at a time until the dough just holds together. Press it firmly into a sheet pan or tart pan, prick the bottom with a fork, and bake at 400°F [200°C] for 10 minutes while you slice the onion.10 min
2. Slice 1 medium onion into thin half-moons. Heat 1 tablespoon oil in a wide pan over medium-high heat, add the onion with a pinch of salt, and stir often until golden and soft, about 8 minutes.8 min
3. Spread the cooked onion over the half-baked crust. Tear 4 oz of the Swiss cheese into shards and scatter it over the onion, then grind pepper over the top.
4. Bake at 400°F [200°C] until the cheese is melted and the crust is golden, about 12 minutes. Let cool for 2 minutes before serving.12 min

Note Swap the onion for 1 cup sliced mushrooms if you prefer. Leftovers keep 3 days covered in the fridge and taste good at room temperature. Serve with a bitter green salad dressed in vinaigrette to cut the richness of the cheese.