1. In a medium bowl, combine the flour and salt.
2. Cut in the butter with a pastry cutter or an electric mixer fitted with the paddle attachment until it is the size of small peas.
3. Sprinkle the water over the dough and mix it lightly to form a dough that holds shape when gently pushed together. Refrigerate for at least 1 hour before using. (This can be made in advance or stored in the refrigerator for up to 2 days or frozen for longer storage.)
4. Roll the dough out until it is 2 inches larger than the pie pan and fit the dough into the pan.
For the tart:
5. Preheat the oven to 350°F. Prick the piecrust with a fork several times and bake until golden brown.
6. Chop 10 of the basil leaves. Mix together with the oil, garlic, salt and pepper.
7. Sprinkle the cheese on the bottom of the pie shell. Arrange the remaining 10 whole basil leaves on top of the cheese.
8. Brush each slice of zucchini and tomato with the basil-garlic oil. Arrange the zucchini and tomato slices alternately, overlapping by half, in a single layer in the pie shell. Brush the entire layer again with the basil-garlic oil.
9. Bake until the vegetables are warmed, about 8 to 10 minutes. Serve warm.