1. To make salsa, place tomatoes and jalapeño pepper, left whole, in a 6-inch or so wide pot and cover with water. Set pot over medium, medium-high heat and bring water to a simmer. Simmer tomatoes and jalapeño pepper until tender, about 10 minutes. Drain water from the pot, reserving 1/4 cup of it. Place drained tomatoes and jalapeño pepper in a food processor or blender and add the garlic, onion and cilantro. Pulse until a smooth salsa is created, adding a bit of the reserved cooking water if you find it too thick. Taste and season salsa with salt. Transfer salsa to a bowl and cool to room temperature. Now cover and refrigerate salsa until ready to serve. Salsa can be many hours in advance (see Note).

2. To cook cod, preheat oven to 425 F. Place cod on a non-stick or parchment-lined sided baking sheet. Combine oil, lime juice, cumin, chili powder, oregano and cayenne pepper in a small bowl. Drizzle the mixture over the fish. Season fish with salt. Bake cod 10 to 12 minutes, or until just cooked through. Remove fish from the oven and cool slightly. While that occurs, heat taco shells in the oven a few minutes. Coarsely flake the fish. Stuff the taco shells with lettuce, flaked fish, avocado, salsa rosa and cheese, and then serve.

Note: This salsa is spicy. If you prefer a milder taste, only use half a medium jalapeño pepper, seeds removed. The recipe yields about 1 1/2 cups of salsa. The leftover salsa you have after using some for the tacos could be served with tortilla chips, for dunking into it. If only large lingcod fillets are available, buy 1 1/4 pounds (560 grams) of them and cut into 4 roughly equal pieces.