Warm the oil in a skillet over medium heat. Add the onion and garlic and saute 5 minutes, until softened. Transfer the onion and garlic to the food processor bowl and add the roasted peppers, tomatoes, ricotta salata and anchovies. Process until pureed. Stir in the parsley and season to taste with salt and pepper.

Toss with hot pasta, stirring in 1/4 cup of the pasta cooking water, and serve immediately, passing Parmesan separately.