Step 1Bring a large pot of water to a boil. Add the shrimp and cook just until they turn a light pink, about 1 minute. Drain immediately and place in an ice bath to cool and stop the cooking process.
Step 2Peel and coarsely chop the shrimp and place in a medium bowl. Toss the shrimp with the lemon juice and set aside for about 1 hour to marinate.
Step 3While the shrimp is marinating, chop the onion, cilantro, tomatoes and habanero pepper, and place in a large bowl.
Step 4After the shrimp has marinated (it should be whitish-pink and firm throughout), drain the shrimp, reserving the liquid. Add the shrimp to the large bowl. Stir in the cumin, pepper, oregano and garlic powder, and season with one-fourth teaspoon salt. Taste, and add back a little of the strained lemon juice to brighten the flavors, and season again, if desired, to taste.