Cook the bucatini following the directions on the package.
Heat the oil in a large skillet over medium heat. Add the pancetta, stirring frequently so as not to burn, until cooked, about 6-8 minutes. Add the onion and garlic and continue until the onions are soft, not browned, about 5 minutes. Add marinara and crushed red pepper and stir until sauce is hot.
Transfer to a large mixing bowl. Add the hot bucatini pasta and combine thoroughly.
Divide among six serving bowls. Finish each with the grated cheese as needed.