Prepare Pastry for Single-Crust Pie. On a lightly floured surface, roll pastry into a circle about 12 inches in diameter. Transfer to a 10-inch tart pan; ease pastry into pan. Trim pastry even with rim of pan. Do not prick pastry. Line pastry shell with a double thickness of foil. Bake pastry in a 450 degree F. oven for 5 minutes. Remove foil. Bake for 5 to 7 minutes more or until pastry is set and dry. Remove from oven. Reduce oven temperature to 325 degrees F. Sprinkle tart shell with Parmesan cheese.
Meanwhile, in a small mixing bowl beat egg whites slightly. Stir in ricotta cheese, garlic, and the 1 tablespoon thyme; spread over pastry.
Overlap large tomato slices in a circle around edge. Arrange yellow cherry tomato slices in a circle within the tomato ring. Fill center with red cherry tomato slices. Stir together olive oil or cooking oil and the 2 teaspoons thyme. Brush tomatoes with oil mixture.
Bake tart in a 325 degree F. oven for 25 to 30 minutes or until heated through and nearly set. Serve warm or at room temperature. Refrigerate any leftover tart.