Step 1

Heat oil in a large high-sided skillet or Dutch oven over medium heat. Add onion and cook, stirring occasionally, until softened, about 2 minutes. Add garlic and cook, stirring, for 1 minute.

Step 2

Add fish, tomatoes and their juices, chile pepper, cilantro, olives, capers, oregano and salt; stir to combine. Add up to 1/2 cup water if the mixture seems dry. Cover and simmer for 20 minutes. Remove from the heat. Serve warm or at room temperature, garnished with avocado (if using).