Combine the capers, sun-dried tomatoes and their oil, the scallions, and garlic in the bowl of a food processor and process until a paste forms, about 1 minute. Season to taste with salt and pepper. Place the fillets in a single layer in a baking dish. Using the back of a spoon, rub the paste all over the tops of the fillets. The fish can be covered and refrigerated at this point for a few hours. Preheat the oven to 400°F. Cover the dish with aluminum foil and bake for about 12 minutes, until the fish flakes apart when pricked with a fork.