This is an awesome summer dish, with bright, spicy flavors and cool, crisp textures. It's quick and simple, and since the shrimp gets chopped into pieces, you can use smaller (cheaper) shrimp to begin with; sizes in the range of 41-50 or 51-60 are just fine. Because we add so many strong flavors, this recipe turns out great with frozen shrimp too.
Since the shrimp is cooked, this is not truly ceviche, the Peruvian dish in which acid from citrus "cooks" otherwise raw fish. Here's a recipe for that sort of ceviche.
Note that the recipe below calls for a tablespoon of Crystal hot sauce, which is a Louisiana product which has more of a vinegary flavor and is not super hot. If you don't have Crystal, substitute one teaspoon Tabasco and two teaspoons vinegar.
1 pound of shrimp, peeled and deveined
1/2 cup freshly squeezed grapefruit juice (substitute lime juice)
1/4 cup ketchup
1 tablespoons Crystal hot sauce (see note above)
2 tablespoons olive oil
2-3 scallions, finely chopped, both white and green parts
1 jalapeño or other hot pepper, seeded and finely chopped, to taste
1/4 cup chopped fresh herbs; cilantro, basil, or a combination of the two works well
1/2 cup finely diced tomatoes
1/2 cup finely diced cucumber
1 teaspoon kosher salt or to taste
Gently poach the shrimp in salted water for a few minutes, until just cooked through. Remove from heat and rinse under cool water to stop cooking. Drain, then chop into pieces in the half-inch to inch range--a size appropriate for serving on a tortilla ship. Set the chopped shrimp aside.
In a large glass or ceramic bowl, add the juice, ketchup, hot sauce, and olive oil, then mix to combine. Stir in the scallions, jalapeño, chopped herbs, tomato, cucumber, and salt. Taste, and adjust seasoning and heat level. Finally, add the chopped shrimp and stir to combine.
Serve immediately, or refrigerate for up to a couple of hours, to allow the flavors to marry. Serve with tortilla chips.