A simple homemade tomato sauce recipe using canned tomatoes, garlic, and onions. You’ll never buy store-bought sauce again! Dairy and gluten free! I buy tomato paste in the tube (usually located on the top shelf above the other tomato pastes). It’s a bit more expensive, but keeps the tomato paste fresh after you open it for a month or so. Here’s a great tip for keeping the canned stuff fresh.