Preheat oven to 400 degrees F (200 degrees C). Lightly grease a 9x13 inch baking pan. Combine 3 cups arugula, garlic, pecans, olive oil, 1/4 CUP Parmigiano-Reggiano cheese, black pepper, and lemon juice in a blender and blend until it reaches the consistency of a pesto sauce. Spread 1/2 cup arugula on the prepared baking pan. Place the tilapia fillets on the arugula. Spread the remaining pesto generously on top of fillets. Sprinkle 1 tablespoon Parmigiano-Reggiano cheese on the pesto. Bake in preheated oven until fish flakes easily, about 20 minutes.