This is a good antipasto dish, or cut into smaller pieces it can be served as hors d’oeuvres. But use the shell as a base and fill with whatever the season offers, such as a lavish assortment of mushrooms, zucchini and asparagus or as simple as potato or squash.
- For the crust:
- 2 cups unbleached all purpose flour
- 1/4 teaspoon salt
- 1 stick (8 tablespoons) unsalted butter
- 4 tablespoons unsalted margarine
- Grated zest (yellow part only without underlying white pith) of one lemon
- 1 teaspoon chopped fresh thyme or ½ teaspoon dried thyme, crumbled
- 4 to 6 tablespoons ice water
- For the filling:
- 4 tablespoons extra virgin olive oil
- 2 cups sliced (1/2-inch) leeks, white and light green parts only, washed well and drained
- 1 cup shredded Pecorino Romano cheese
- 2 tablespoons chopped fresh oregano leaves
- 2 medium-size, ripe but firm tomatoes, cored, cut in half and sliced 1/4-inch-thick
- Salt and freshly ground black pepper to taste
- Fresh oregano sprigs, optional
Make the crust: In the work bowl of a food processor fitted with the metal blade, combine the flour and salt. Add the butter, margarine, lemon zest and thyme. Process, using quick on/off motions, until the mixture resemble very coarse meal, about 10 seconds total. Sprinkle 4 tablespoons of the water over the flour mixture and process just until incorporated. The dough should just hold together in the bowl, but not be wet or sticky. If not, add enough of the remaining ice water a little at a time, processing very briefly after each addition, until the dough is the proper consistency. Turn the dough out onto plastic wrap and knead it lightly into a ball. Wrap the dough securely and chill at least one hour or up to two days before continuing.
On a lightly floured board, roll out the dough to a 12-inch circle about 1/8-inch-thick. Fold the dough circle in half and place over half of a 10-inch tart pan with a removable bottom. Unfold the dough and gently press the dough into the corners and along the sides of the pan. Trim any overhanging dough to an even 1/4-inch. Fold this overhanging dough over and tuck it between the dough and the sides of the pan to form a lip of double thick dough around the sides of the crust. Press an empty tartlet pan on top of the dough to prevent the crust from puffing up while baking. (Alternatively, you may line the dough with aluminum foil and fill the crust with 2 cups uncooked rice or beans, spread into an even layer.) Chill the dough at least 30 minutes.
Preheat the oven to 375 F.
Meanwhile, prepare the filling ingredients: In a medium-size skillet, heat 2 tablespoons of the oil over medium heat. Add the leeks and cook, stirring often, until tender, about 10 minutes. Season the leeks with salt and pepper and set aside. In a small bowl, toss the grated cheese and oregano and set aside.
Bake the weighted tart shell 15 minutes. Carefully remove the inner tart pan or aluminum foil and weights. Poke the bottom and sides of the crust at 1/2-interval with a fork and return the tart shell to the oven. Bake until light golden brown, 15 to 20 minutes. Remove and cool completely.
Spread the leeks in an even layer over the bottom of the tart shell. Arrange the tomato slices overlapping in concentric circles of the leeks. Season the tomato slices with pepper and drizzle with the remaining 2 tablespoons olive oil. Sprinkle the grated cheese mixture over the tomatoes, return the tart to the oven and bake until the cheese is light golden brown, about 15 minutes.
Serve warm, decorated with a sprig of fresh oregano.