Not all "red sauce" is created equal; pizza sauce and tomato sauce for pasta actually have distinct characteristics that make them less interchangeable than you might have thought.

Pizza sauce and basic red sauce for pasta are both made with tomatoes, but pizza sauce is often thicker and less watery, whereas pasta sauce has a higher water content.

To make pasta sauce into pizza sauce, strain some of the liquid or add it to a pot and reduce until some moisture has evaporated; the sauce will cook down and become thicker.

While cooking, incorporate pizza seasonings like oregano, garlic powder, and crushed red pepper flakes, then blend to smooth, and thicken with tomato paste or cornstarch as needed.

Make pizza sauce into pasta sauce by adding a little water. You can also sauté garlic and onion in butter or oil, then add the pizza sauce along with a splash of water.