Place fish and shrimp in a bowl and season with lime juice, salt, and pepper; marinate for 20 minutes.
In a large clay pot or heavy-bottomed skillet, heat olive oil and 1 tablespoon of dendê oil over medium heat.
Add onions and garlic, sautéing until translucent.
Layer half of the bell peppers and tomatoes over the onions.
Arrange the marinated fish and shrimp in a single layer over the vegetables.
Layer the remaining bell peppers and tomatoes on top of the seafood.
Pour the coconut milk and the remaining tablespoon of dendê oil over the layers.
Cover the pot and simmer on medium-low heat for 15 to 20 minutes until the fish is flaky and cooked through.
Remove from heat and garnish with chopped cilantro and scallions before serving.