Squeeze ½ lemon over salmon and let it rest for 10 minutes at room temperature. Meanwhile, in a medium saucepan, combine balsamic vinegar, white wine, honey, dijon mustard, ½ teaspoon rosemary, and garlic. Heat mixture over medium-high heat and bring to a boil, then reduce heat and simmer over medium-low heat until sauce has thickened, about 5-7 minutes. Stirring occasionally. Remove from heat and set aside.