Finely chop the tomatoes, onions, and cilantro.
Carefully remove the stem, ribs and seed from the jalapeno pepper and finely chop it. I use food gloves when working with jalapeno peppers as the juices can irritate skin for hours. Avoid getting jalapeno chile juice on your face or in your eyes.
Place tomatoes, onions and cilantro in a serving bowl. Add half the chopped jalapeno pepper and mix well. Add salt and pepper to taste. If the salsa is not hot enough, add some more.
Let the salsa sit for an hour at room temperature for the flavors to develop. Store in a refrigerator for up to 3-5 days.