What is the main ingredient in traditional pesto sauce?

The main ingredient in traditional pesto sauce is basil. This herb is central to pesto's distinct flavor and aroma, contributing the characteristic taste that defines this Italian sauce. Pesto is traditionally made with fresh basil leaves, which are blended with pine nuts, garlic, Parmesan cheese, olive oil, and salt. The vibrant green color and aromatic profile of pesto come primarily from the high proportion of fresh basil leaves used in the preparation.

While garlic, parsley, and cilantro can enhance or be used in variations of sauces, they do not constitute the core of traditional pesto. The use of basil is essential, as it embodies the essence of this classic Mediterranean preparation, making it the key ingredient that distinguishes pesto from other herb-based sauces.