Preheat oven to 450°F. Mince the garlic in a food processor. Add in the walnuts and process until walnuts are a fine consistency. Add in cilantro until mixture is thick and pasty. Drizzle in olive oil and process until blended.
Place salmon on a foil-lined baking tray. Season both sides with salt and pepper. Spread the walnut mixture evenly over the fish. Bake salmon for 20 minutes or until fish flakes easily with a fork. Garnish with fresh lemon slices.