Cook the beans by your preferred method. I like to soak them overnight and then cook them for 45 minutes in the instant pot.
Preheat oven to 300℉.
Heat a large Dutch oven over medium-high heat. Add in the sliced bacon. Cook until bacon begins to render fat and then stir in the chopped onion. Sauté bacon and onions together until onions begin to soften and the bacon is browned and slightly crisp. This should take about 5-6 minutes. After browned, drain off the excess grease that the bacon has rendered.
Mix together tomato sauce, brown sugar, molasses, maple syrup, dried mustard, vinegar, apple juice, water, and salt until well combined. Add to bacon and onion mixture and add cooked beans and gently stir to combine.
Beans should be pretty well submerged in liquid and the mixture should be relatively loose. If there does not seem to be enough liquid in the baking dish, add up to ½ cup of additional water or juice. Cover the Dutch oven with oven-safe lid or foil.
Bake covered for 2 hours. After 2 hours, remove the lid or foil, and bake for another 30-40 minutes, or until thickened.
