Spaghetti with Spaghetti Squash and Pancetta

Name: Spaghetti with Spaghetti Squash and Pancetta
Ingredients: 1 spaghetti squash, about 2 pounds; 3 tablespoons olive oil, divided; Kosher salt + freshly ground black pepper; 1 pound spaghetti; 4 ounces thick-cut pancetta or bacon, cut into cubes; 1 small onion, chopped (about 1 cup); 1 tablespoon finely chopped fresh sage; 1/4 teaspoon red pepper flakes, or to taste; 2 tablespoons diced preserved lemon peel (from about 1/2 a large preserved lemon); 1 cup finely grated pecorino romano (parmesan can be substituted), plus more for serving