Serves 6 to 8
1 9-inch tart pan lined with pie crust (store-bought is a great shortcut)
3 large tomatoes, cut into 1/2 -inch thick slices
1/4 cup Dijon mustard
1 cup coarsely grated Gruyere cheese
2 tbsp. chopped fresh basil
1 garlic clove, minced
2 tbsp. extra-virgin olive oil
Kosher salt and freshly ground black pepper
Preheat oven to 375°F.
Line the pastry with parchment paper and fill with pie weights or dried beans. Bake until the crust is set, 8 minutes. Remove the paper and weights and bake until golden brown, about 10 more minutes. Remove from the oven and cool on a wire rack.
Sprinkle the tomatoes with salt and drain in a colander for 10 to 15 minutes.
Turn up the oven to 400°F.
Spread the mustard over the bottom of the pie crust and sprinkle the cheese over it. Arrange the tomatoes over the cheese in 1 overlapping layer. Bake until the pastry is golden brown and the tomatoes are very soft, 25 to 30 minutes.
In a small bowl, stir together the basil, garlic and olive oil. Season with salt and pepper to taste. Sprinkle the pie with this mixture while hot and spread out gently with the back of a spoon. Serve the pie hot or at room temperature.