Tomato, Basil and Cheese Baked Pasta

INGREDIENTS

• 1 cup store bought basil pesto sauce
• 2 tablespoons extra-virgin olive oil, 2 turns of the pan in a slow stream
• 1 (28-ounce) can crushed Italian tomatoes, any brand
• 1/2 cup, 10 to 12 fresh basil leaves, torn into small pieces
• 1/2 cup grated Parmigiano-Reggiano, a couple of handfuls
• 1/2 small to medium yellow onion
• 3 large cloves garlic
• Salt and pepper
• 1 pound small shell pasta
• 1 cup ricotta cheese
• 1/2 pound fresh mozzarella