Rocoto peppers are available at many Latin markets. You can substitute a red jalapeño or Fresno pepper.
1 rocoto pepper, stem removed
25 1/4 ounces striped sea bass, divided
1/4 cup chopped red onion
3/4 cup fresh lime juice (about 5 limes)
1/2 teaspoon kosher salt
2 garlic cloves
1 (2-inch) piece celery
1 (1-inch) length peeled fresh ginger, sliced
1 cup thinly vertically sliced red onion
1 tablespoon chopped fresh cilantro
How to Make It
Boil rocoto pepper 1 minute; drain. Repeat twice. Combine 1 1/4 ounces pepper flesh (reserve remaining pepper for another use) and 1 teaspoon pepper seeds, 1 1/4 ounces fish, 1/4 cup chopped red onion, juice, salt, garlic, celery, and ginger in a blender. Process until smooth. Chill rocoto mixture for 20 minutes.
Combine chilled rocoto mixture, remaining 24 ounces sea bass, sliced red onion, and cilantro in a bowl; toss to combine. Serve in chilled bowls or glasses.