1 large onion, sliced as thin as possible (2 cups)
Pastry for 9-inch pie crust, homemade or purchased
4 oz. goat cheese, crumbled (1 cup)
2 tsp. coarsely chopped fresh thyme or 1/2 tsp. dried
3 medium tomatoes, cut into 1/4-inch-thick slices
Preheat oven to 450°F. In medium skillet, heat oil over medium-high heat. Add onion and cook, stirring often, until golden brown, 8 to 10 minutes. Season to taste with salt and pepper. Remove from heat.
Lay pastry dough flat on an ungreased baking sheet. Distribute onion evenly on top, leaving 1-inch border all around. Dot with goat cheese, sprinkle with thyme and some pepper. Starting from outer edge of onion, arrange tomato slices on top, overlapping slightly. Sprinkle with salt and pepper. Fold pastry over topping, crimping dough every inch or two.
Bake until crust is golden, 18 to 20 minutes. Transfer to wire rack to cool slightly. Cut into 4 wedges and serve.