Start by chopping the ripe tomatoes into bite-sized pieces and placing them in a mixing bowl.
Next, peel and dice the cucumber into small cubes, then add it to the bowl with the tomatoes for a crunchy texture.
Finely chop the fresh cilantro leaves and stir them into the mixture to add herbal brightness.
Squeeze fresh lime juice over the chopped ingredients, feeling the citrusy aroma as you do so.
Add finely minced chili for heat, adjusting the amount based on your spice preference.
If using, stir in the finely chopped red onion for extra sharpness and crunch.
Mix all the ingredients thoroughly with a spoon, breaking up the tomatoes slightly to release their juices.
Season the salsa with salt and black pepper to taste, then give it a final stir to evenly distribute.
Let the salsa sit for a few minutes to allow flavors to meld and the textures to soften slightly.
Serve the fresh salsa in a colorful bowl, garnished with extra cilantro if desired.