Cook bacon in a large skillet over medium-high heat, until crispy. Transfer cooked bacon to a paper towel-lined plate, then remove all but 1 tablespoon of bacon fat from skillet.
Add sliced onion to skillet and cook for 15 minutes, stirring every few minutes, until dark and beginning to caramelize.
Pour in bourbon and scrape up any brown bits from bottom of skillet, then add in maple syrup and balsamic vinegar. Cook 3-5 minutes or until thick and syrupy.
Add cooked bacon back into skillet along with pinch of cayenne pepper, cook for an additional 5 minutes then let cool slightly.