Place the red onion, garlic and fresh jalapeño (if using) into a food processor and pulse 2 – 3 times. Scrape down the sides and add the remaining ingredients. Pulse a couple more times until desired texture is reached. Taste for seasoning.
Store leftover salsa in a sealed, airtight container in the fridge for 5 -7 days.
*If you love spicy, feel free to add the jalapeño seeds.