Mix the sugar, salt, garlic powder and pepper in a small bowl. Brush the salmon with water to moisten it. Sprinkle both sides of the salmon with all the sugar mixture. Melt the butter in a large, heavy skillet over medium high heat. Add the salmon and cook until it is crusty on the outside and just opague in the center, about 4 minutes per side.Transfer each fillet to a warm plate. Add the clam juice and half and half or cream to th skillet.Boil until the sauce thickens enough to coat a spoon, scraping up the brown bits, about 4 minutes. Spoon sauce over the salmon. Sprinkle with green onions for garnish. Serve and enjoy!