Tomato paste is basically tomatoes that have been cooked down and concentrated until they’re a thick, deep-red brick of flavor. It’s intense, slightly sweet, and used to add body and umami to sauces, stews, and soups.
Tomato sauce, on the other hand, is already a finished product. It’s thinner, often seasoned with herbs, garlic, or sugar, and designed to be spooned straight onto pasta. So when you sub sauce for paste, you’re adding volume and moisture that the original recipe didn’t plan for.
