For the Glaze: Whisk all ingredients together in a small saucepan and simmer over medium-high heat until thickened, about 1 minute. Remove from heat and cover.
For the Salmon: Adjust oven rack to middle position and heat oven to 300°F/150°C.
Combine sugar, salt, cornstarch, and pepper in small bowl. Pat the salmon dry with paper towels and rub sugar mixture evenly over flesh side of salmon.
Heat oil in 12-inch oven-safe nonstick skillet over medium-high heat until just smoking. Lay salmon, flesh side down, in skillet and cook until well browned, about 1 minute. Using tongs, carefully flip salmon and cook on other side for 1 minute.
Remove from heat and spoon the glaze over the fillets. Transfer skillet to oven and roast until center is still translucent, about 7-10 minutes. Serve.