Combine all the ingredients in a bowl. If you prefer a smoother texture―more like jarred―pulse half the salsa in a food processor, then combine it with the remaining chunky half. Cover tightly and refrigerate for up to 5 days.
This homemade salsa works as a condiment but also as a side dish―think of it as a chopped tomato salad. If you want a smokier version, briefly grill the tomatoes, onion, garlic, and jalapeño over high heat before proceeding.