Heat oven to 450 degrees F. Coat a baking dish with nonstick cooking spray.

Pesto: Into the bowl of a food processor, combine 1/2 cup of the walnuts, arugula, parsley, sun-dried tomatoes, garlic and salt. Pulse until coarsely chopped. With machine running, gradually drizzle in the olive oil and process until smooth. Stir in the cheese. Separate 3/4 cup of the pesto for this recipe. Reserve the rest for another use.

Fish: Place fillets flat on a work surface. Spoon 1 tablespoon of pesto over each fillet. Fold in half and place into the prepared baking dish. Season the fillets with the salt and pepper and place a few lemon slices over the top of each. Bake at 450 degrees F for 20 minutes, or until fish is cooked through and flakes easily with a fork.

While the fish is baking, cook pasta following package directions. Drain pasta, reserving 1 cup of the cooking water.

Toss pasta with remaining 1/2 cup pesto. Gradually stir in the pasta water until all the pasta is evenly coated.

Serve pasta immediately, topped with flounder. Garnish with remaining nuts.