Combine chopped tomato, onion or red onion, a bit of garlic if you like, a hot chile pepper two depending on how spicy you like it, salt to taste, and chopped fresh cilantro if you like it. You can splash on a bit of fresh lime juice or red wine vinegar, if you're so inclined.
How much of each? Well that is what makes salsa fresca so fabulous - it really depends on how you like it and what you have on hand. I find 4 tomatoes, a half an onion, a small clove of garlic, 1 chile, and a handful of cilantro suits me and my taste, so you can start from there and find your own secret combination.
