Cut up tomatoes, remove the seeds, then dice and put in large bowl
Dice the onion, add to bowl
Mince the garlic, add to bowl
Rinse cilantro, tear from stems, rough chop, add to bowl
Add salt, pepper, ground cumin to taste... I usually go a little heavy on the salt (kosher) to help pull water from the tomatoes, easy on the pepper, and somewhere in between on the cumin. Be careful with the cumin, you can add more later if necessary.
Cut the lime in half, juice into the bowl.
Stir all ingredients together, let sit at room temperature for a couple of hours. After about one hour taste to see if the flavors are coming together well and add more to the bowl if necessary. After a couple hours you are ready to go.