Pasta with Roasted Tomatoes
1/4 cup plus 6 tablespoons extra-virgin olive oil
1 Vidalia (or other sweet) onion, finely sliced
9 to 10 fresh plum tomatoes
Salt and freshly ground pepper
2 cloves garlic, pressed through a garlic press, or 1/2 teaspoon garlic powder
2 1/2 tablespoons finely grated Parmesan cheese, plus extra for serving
2 1/2 tablespoons finely grated pecorino cheese
1 pound penne pasta