1 tablespoon olive oil
1 small white onion, minced
2 garlic cloves, minced
1/4 teaspoon red pepper flakes
1 teaspoon kosher salt plus more to taste
1/4 teaspoon black pepper plus more to taste
1-28 ounce can crushed tomatoes
Parmesan rind, optional
1 pound dried rigatoni
Grated Parmesan and chopped parsley for serving
In a large saucepan, heat the olive oil over medium heat. Add the onions and sauté until they soften, about 5 minutes. Add the garlic, red pepper flakes, salt and pepper and cook until fragrant, about 2 minutes. Add the tomatoes and Parmesan rind, if using, and bring the mixture to a boil. Reduce the heat to simmer for 10-15 minutes until the sauce has thickened.
Cook the rigatoni according to package instructions. Reserve 1 cup of pasta water. Stir the rigatoni into the sauce and add the pasta water by the 1/4-cupful to thin the sauce. Season to taste and top with grated Parmesan and parsley before serving.
If you prefer a smoother sauce, puree it in the blender.