Hi there - I change things around a lot according to tastes. You can add chillies or jalepenos if you like it to be a bit spicier. but this is how I do it for the whole family.
Dice 2 medium Tomatos
Dice 1/2 Onion (I like the purple ones best)
Chop 1/2 cup fresh cilantro
1 TBSP lemon juice
season with 2 tsp cumin and salt and pepper to taste
I like to let it sit for a couple of hours and let the flavours blend. Personalize any way your like - more onions? More tomatoes. It's all good.