Heat a large skillet over medium high heat. Chop your bacon into 1/2" chunks and thinly slice onions.
Add bacon to hot skillet and cook until almost completely crisp, stirring occasionally to ensure even cooking. Drain off all but 2 tablespoons of bacon grease.
Turn the heat down to medium low, and add in sliced onions and stir to coat completely. Cook until beginning to soften, 2 to 3 minutes.
Add all the remaining ingredients and stir until sugar is dissolved. Allow to cook slowly until onions are deep golden brown and jam is thickened.
Eat immediately or store in the refrigerator for up to 2 weeks, or freeze up to 3 months. Yields about 2 cups.