Wash the serrano peppers under cold water and remove their stems.
Add serrano peppers, onion, cilantro, garlic, olive oil, lime juice, and salt to a food processor or blender.
Pour ⅓ cup water and blend to your desired consistency.
Adjust salt and lime juice to taste then transfer the salsa to a bowl or jar.
Serve with your favorite foods or store for up to 7 days in the fridge.
Notes
Want the flavor of serrano chili pepper but not the spiciness? Cut them longwise and remove seeds and membranes to tone down the spiciness without compromising the flavor.
The longer you blend, the smoother the sauce will be, but since is made with raw ingredients it still has a lot of texture.
If you don't like the texture of raw garlic or don't want to find the small bits here and there, blend it first with 1-2 chilies and water until nicely pureed, then add the remaining ingredients and blend to your desired consistency.