Make the romesco sauce: In a food processor, combine the red peppers, almonds, bread, vinegar, honey and smoked paprika. Pulse to combine. With the motor running, add the olive oil and puree until combined. Season with salt and pepper to taste.
Make the fish: Preheat an outdoor grill or a grill pan to medium high. Drizzle the tuna with the olive oil and generously season with salt and pepper on both sides. Grill for about 2 minutes on each side. Remove from the grill, tent with foil and let stand for a few minutes. Thinly slice the tuna and serve with the romesco sauce.