Finely chop the red onion, chili pepper, and cherry tomatoes, then set aside.
Place the peeled shrimp in a mixing bowl and squeeze fresh lime juice over them, ensuring they are fully submerged.
Stir the shrimp gently to coat them evenly with the lime juice, then let them marinate for about 15 minutes until they turn opaque and firm.
Add the chopped red onion, chili pepper, chopped cilantro, and halved cherry tomatoes to the marinated shrimp, folding everything together gently.
Give the ceviche a final stir and taste it; adjust the lime or chili if needed for extra brightness or heat.
Chill the ceviche for another 10 minutes if desired, then serve cold in small bowls or glasses, garnished with extra herbs if preferred.