Preheat your oven to 350°F (175°C). Spray a 2 to 3-quart casserole dish with cooking spray.

Heat a large skillet over medium-high heat and add the diced bacon. Cook for 4-5 minutes until crispy.

In the same skillet, add finely chopped onion and cook for 5-6 minutes until soft and translucent.

In the prepared baking dish, combine undrained baked beans, sautéed onions, three-quarters of the bacon, ketchup, brown sugar, mustard, molasses, Worcestershire sauce, and apple cider vinegar. Mix thoroughly.

Sprinkle the remaining crispy bacon on top of the bean mixture.

Bake uncovered for about 1 hour, until bubbling and shiny on top.

Let cool slightly and serve warm.