Seviche-Style Shrimp and Avocado Tacos

Look for cooked peeled shrimp on the seafood counter; or quickly defrost frozen cooked peeled shrimp in a colander under cold running water. Marinate the shrimp in a non-reactive dish, such as glass or ceramic; in aluminum or copper dishes, the citrus juice will react, giving the shrimp a metallic taste.
Grate the lime zest, measure out 1 tablespoon; measure out the lime juice for 1/4 cup. Put the peel and juice in a large bowl. Add tomatoes and other ingredients, except tortilla; mix well to combine. Cover and refrigerate for 15 minutes, stirring occasionally.Preheat the tortillas according to the instructions on the package. Place about 1/2 cup shrimp mixture in the center of each tortilla; fold in half. Serve immediately.