The primary ingredient in a traditional spaghetti sauce is tomatoes. Typically, fresh or canned tomatoes are used as the base, providing acidity and sweetness that form the foundation of the sauce. Ingredients such as garlic, onions, olive oil, herbs (like basil and oregano), and sometimes meat, are added to enhance flavor and complexity. The simplicity of the dish allows for variations, with countless family recipes existing around the world. A traditional spaghetti sauce often simmers for a while to deepen flavors, making it a staple in Italian cuisine.