A specialty of the Catalan region of Spain, romesco sauce is a fragrant, garlicky blend of ground almonds, garlic, tomatoes and peppers. Roasting the red pepper and tomato gives this sauce its deep flavor. If you do all the roasting the day before, the cooking takes just a few minutes once you thread the skewers.
1. Preheat the oven to 400 F or preheat the grill.
2. In a baking dish, combine the olive oil, salt and pepper to taste, and lime juice. Add the salmon and scallops to the dish and stir with a wooden spoon to coat all the pieces. Cover and refrigerate while you make the sauce.
3. For the Romesco Sauce: In a blender, combine the roasted pepper, tomatoes, almonds, garlic, vinegar, and olive oil, blending until smooth. Season with salt and pepper to taste and set aside.
4. Remove the salmon and scallops from the marinade and discard the liquid. Pat dry each scalllop and chunk of fish with paper towels.
5. Thread each skewer with 2 onion chunks, 1 salmon chunk. bell pepper and poblano chunks, and 1 scallop.
6. To Bake or Broil: Set the skewers on a baking sheet and place on the top rack of your oven. Bake or broil for 4 minutes, then rotate the baking sheet in the oven and give each skewer a half turn. Bake or broil for another 4 minutes, or until the salmon is firm to the touch and the scallops have begun to brown on the edges.
7. To Grill: These cook quickly, so it's best to set them to the side of the grill and not directly over a flame. Cook for 2-3 minutes, then turn. Turn the skewers gently so that the fish doesn't break and fall into the fire. When the salmon feels firm to the touch and the scallops show light grill marks, remove from the grill.
8. Arrange two skewers on each plate and spoon the sauce over them, or pile the skewers on a serving platter and serve the sauce in a bowl.