Heat the olive oil in a large pot over medium heat. Add the sliced onion and cook for 3 minutes until it begins to soften.
Add the sliced bell peppers and minced garlic. Cook for another 4 minutes, stirring occasionally, until the peppers start to soften.
Stir in the drained diced tomatoes, salt, and black pepper. Cook for 2 minutes to let the flavors combine.
Pour in the coconut milk and bring the mixture to a gentle simmer. Do not let it boil hard.
Add the fish pieces to the pot. Spoon some of the broth over the top, cover, and simmer for 6 to 8 minutes until the fish flakes easily with a fork.
Remove the pot from the heat. Stir in the lime juice and chopped cilantro just before serving.