Marcella Hazan’s famous tomato sauce with onion and butter, from her book “The Essentials of Classic Italian Cooking,” transforms three simple ingredients into a luscious sauce. Our pantry-focused version replaces the fresh tomatoes with a can of tomato paste to create a dish that can be on the table in minutes. To enhance the sweetness and umami, we finish the sauce with a splash of balsamic vinegar and nutty Parmesan cheese. If you don’t have spaghetti, use another type of pasta, such as fettuccine or linguine. Fresh basil, though an optional garnish, is a great addition; if you have it on hand, toss some into the pasta just before serving.