Lemon Pesto can be used as topping or pasta sauce and can be served cold or gently warmed. Typically, pesto should not be cooked or simmered because it is meant to be a fresh condiment. High heat will greatly change the flavor of the ingredients and take away from the clean natural taste of fresh ingredients. When warming, the hot pasta and reserve pasta water heat lemon pesto just enough to release the vibrant flavor and help the ingredients combine.