Preheat oven to 425°.
Heat oil in a nonstick skillet over medium- high heat. Add lemon grass, shallots, and garlic; sauté 3 minutes or until tender. Remove from heat; stir in soy sauce and red pepper.
Place lemon in an 11 x 7-inch baking dish coated with cooking spray; arrange fillets over lemon slices. Spoon lemon grass mixture evenly over fillets. Bake at 425° for 15 minutes or until fish flakes easily when tested with a fork. Sprinkle with cilantro and green onions.