Peruvian
Cut the very fresh, well-chilled fish into even bite-sized cubes.
Rinse the sliced red onion in cold water to soften its sharpness, then drain.
Combine the fish with lime juice, garlic, chili, and salt, making sure the fish is submerged.
Let it cure in the refrigerator until the fish turns opaque, about 10 to 15 minutes.
Fold in the red onion and most of the cilantro just before serving.
Taste and adjust salt and lime, then plate with the remaining cilantro.
Serve cold, traditionally with boiled sweet potato or corn on the side.