In a medium saute pan with the olive oil, saute the onions and garlic. When the onions are translucent, add the shrimp and continue to saute for 3 to 4 minutes. Then add the tequila and flame off the alcohol. Then add the tomatoes and saute for another 3 to 4 minutes. Then add the lime juice when the shrimp is cooked half way.
When shrimp is fully cooked, fold in the cilantro and avocado. Season with salt and pepper and serve.