This is my recipe, you can scale to your needs.
5 Large tomatoes, diced(I use Better Boy)
4 Medium white onions, diced
3 Large Jalapenos, diced
3 Serranos, diced
1 bunch of cilantro, finely chopped
3 cloves garlic, finely chopped
Juice from 2 limes
Zest from 1 lime
1 tsp salt
Combine all ingredients in bowl. Best when allowed to set in the fridge for 24hrs to allow the flavors to meld.