Mix all of the ingredients together. Do a taste test to make sure you can taste the salt. Salt is important because it helps to inhibit the growth of bad bacteria.
Put the salsa in a quart jar. Gently press down so everything is under liquid. Use a weight, piece of onion or bell pepper to keep the salsa ingredients submerged. Put on a lid and open the lid at least once per day.
Let the jar sit on the counter for 2-5 day (it ferments quicker in warm temperatures and slower in cool temperatures). You'll know it's fermenting when bubbles start to appear when you stir it. When the salsa starts to taste tangy, it is ready to eat. Store the fermented salsa in the fridge.