Place diced avocados into a large bowl. Squeeze juice from half of a lime over the avocados to prevent them from browning.
Slice the tomatoes in half lengthwise and scoop out the seeds and juices, so just the firmer flesh remains.
Dice tomatoes and add them to the bowl, along with the finely minced cilantro, jalapenos and onions. Season with 1/2 teaspoon of salt and 1/4 teaspoon of black pepper and stir to combine well.
Add lemon juice, more lime juice, and salt and pepper to taste.
Serve with tortilla chips, tacos, burritos and more.