Preheat oven to 400, place top rack 8" from the bottom of your broiling until. Line a baking sheet with a large piece of foil (large enough to wrap over the top of your salmon--you can also use a second sheet on top).
Place salmon on baking sheet, and allow the filet to come to room temp as you make the sauce.
Place brown sugar, water, bourbon, soy sauce, red wine vinegar, garlic, 1/2 teaspoon salt, and 1/4 teaspoon pepper in a small saucepan and reduce until thick and sticky--should be 5-7 minutes. Allow sauce to cool for 15 minutes, then set aside 2 tablespoons of the sauce.
Sprinkle the salmon with remaining 1/2 teaspoon kosher salt and 1/4 teaspoon black pepper. Brush the salmon with sauce. Then cover with foil, leaving enough room for steam to circulate around and over the salmon.
Bake until the thickest part of your salmon still has a few minutes longer to cook--will be between 12-16 minutes, but this depends on how thick your salmon is.
Turn your oven broiler to high. Remove the top layer of foil so the top of your salmon is exposed, and place your baking sheet on the top rack. Broil until the salmon is cooked through (should flake easily at the thickest part), and your glaze has started to caramelize, about 3-4 minutes.
Serve immediately with set aside sauce and green onions. Enjoy!