In a medium pot, bring 4 cups of water to boil, turn off the heat, drop in the shrimp and cover. Leave the shrimp in the hot water for 1 minute. Drain off the water and place the shrimp in a large bowl.
Soak the red onions with warm water for about 5 minutes, rinse and drain.
Add all the ingredients to the shrimp, mix well and let it sit in the fridge for at least one hour. Serve cold with saltine crackers, patacones or plantain chips.