Remove skin from onion and slice into 1/4" slices. Evenly cover the bottom of a non stick skillet with onion slices. Sprinkle with salt and pepper. Lay salmon on top of onion slices. (If salmon has skin, place skin side down.) Sprinkle lemon pepper evenly over salmon. Slice lemons in 1/4" slices and layer evenly over salmon. Spread dill sprigs over lemon slices. Drizzle the whole pan with olive oil. Turn stove to med-high heat until pan is heated and onions start to sizzle. Cover the pan with a lid and reduce heat to med-low. Cook, covered, for 15 minutes or until the fish flakes easily with a fork. Cut fish into portion sizes and serve each piece of fish with an onion , a lemon slice, and a sprig of dill.