Combine tomatoes and boiling water; let stand 30 minutes. Drain; thinly slice, and set aside.
Combine oil and garlic in a small bowl; stir well. Combine 1 teaspoon oil mixture, potato slices, salt, and pepper in a bowl; toss well. Arrange potato slices in a single layer on a baking sheet. Bake at 350° for 10 minutes or until tender. Set aside.
Brush prepared Pizza Dough with remaining oil mixture. Arrange onion slices over dough, and top with sliced tomato. Arrange potato slices over tomato; sprinkle with cheeses. Bake at 500° for 10 to 15 minutes or until crust is golden. Remove from oven; sprinkle with sage.