First, peel the onion and cut it in half. Then, add the onion and garlic cloves to the bowl of a food processor.
Chop the onion and garlic, then roughly chop one jalapeño and add it to the food processor. (Exclude the membrane and seeds to reduce the heat.)
Chop the jalapeño with the onions/garlic.
Next, add tomatoes then cilantro to the food processor.
Chop the tomatoes and cilantro to your desired consistency.
This next step is optional, but I like to do it - pour the salsa into a fine metal strainer over a bowl to get rid of any excess moisture. (The tomatoes and onions release a lot of liquid when you chop them up.) You want to do this BEFORE adding the salt and lime juice because you will strain out the salt and lime otherwise.
Return the strained salsa to a bowl (or the food processor), then add salt and the juice of a lime.
Mix well, then taste. Adjust with more salt, lime, and cilantro if needed. Serve with tortilla chips.