The classic fresh salsa of diced tomato, onion, serrano chile, and cilantro — Mexico's flag in a bowl. This vegetarian, fresh condiment adds healthy, vibrant flavor to any family dish.
Dice the roma tomatoes into small, even cubes, discarding the seeds if desired for lower moisture.
Finely chop the white onion and add it to a medium mixing bowl for even distribution.
Slice the serrano chiles lengthwise; remove seeds for milder heat, or keep them for spicier salsa, and mince finely.
Roughly chop the fresh cilantro leaves, avoiding woody stems, and add to the bowl.
Pour in the lime juice and sprinkle with kosher salt, then gently toss everything together with a spoon until just combined. Let sit for 10 minutes to meld flavors before serving.