Mix together onion, and ½ teaspoon salt and let sit 10 minutes.
Peel and add avocado, mashing to desired consistency, add lime juice to taste (minimum 2 tablespoon to prevent browning, up to 4 tablespoon for extra zip). Add finely chopped tomatoes and stir through.
Season to taste with salt and pepper and serve with tortilla chips.
Notes
*This can easily be doubled or tripled depending how many avocados you want to use, just err on the side of less salt until seasoning at the end.