Preheat cast-iron or other flame-proof skillet on grill set to high. Add oil, onion and garlic. Close lid and cook, stirring occasionally, about 7 min. until onion starts to soften.
Add shrimp, smoked paprika, salt, and hot pepper flakes. Cook, stirring constantly, 2 min. until shrimp starts to turn pink and curl. Stir in tomato; cook 1 to 2 min., or until shrimp are cooked through.
Using oven mitts, remove skillet from heat. Stir in lemon juice and parsley. Serve shrimp with cooked rice or quinoa, in lettuce cups or as a warm appetizer with crusty bread.
To clean a cast-iron skillet, hand wash and immediately dry. Rub a little oil on the insides of the skillet. This light coating will protect the pan from moisture and rust.