Heat a non-stick pan over medium heat. Add butter, once melted, add onions. Cook until soft, about 10 minutes.
Add garlic and cook about 1 minute, then add brown sugar and stir using a wooden spoon.
Add the remaining ingredients (vinegar, ketchup, lemon juice, Worcestershire sauce and salt) and let it come to a simmer.
Preheat oven to 375. Place chicken breast in a baking dish and pour sauce over the chicken. Bake until internal temperature of 165 is reached. 20-30 minutes depending on the thickness of the chicken breast.
Enjoy with mashed potatoes and veggies for the ultimate comfort meal!