Chop 1/2 onion finely and put
it in a fine mesh strainer. Rinse onion under running
water and soak in water for 5 minutes. Press onion in the strainer
to get rid of as much water as you can.
Cut avocados in half. Remove seeds.
Scoop the meat with spoon. Put it in a bowl and mash until it becomes
puree.
Finely chop serrano chile, cilantro, 1/2 tomato, and garlic and add
to the mashed avocado.
Add and mix in remaining ingredients.
Garnish with chili powder.
Serve with tortilla chips.