Start by placing the peeled and deveined shrimp in a mixing bowl. Pour the fresh lime juice over the shrimp, making sure they are fully submerged. Cover and refrigerate for 15-20 minutes until the shrimp turn opaque and firm to the touch, absorbing the citrus flavor.
While the shrimp marinates, prepare the vegetables. Thinly slice the red onion and set aside. Dice the ripe tomatoes, removing excess seeds, and place in a separate bowl. Slice the jalapeño thinly, removing seeds for less heat if desired.
Once the shrimp are opaque and firm, drain them slightly if needed, but keep most of the lime marinade in the bowl. Gently fold in the chopped tomatoes, sliced red onion, and jalapeño slices. Stir carefully to combine all the vibrant ingredients.
Add freshly chopped cilantro to the mixture, then season with salt and pepper to taste. Give everything a gentle stir, making sure the herbs and seasonings are evenly distributed. Let the ceviche sit for an additional 5 minutes for flavors to meld.
Taste the ceviche and adjust salt or lime juice if needed. Serve immediately in chilled bowls or glasses, garnished with extra cilantro if desired. Enjoy this bright, citrusy seafood dish with tortilla chips or on its own for a refreshing treat.