Preheat oven to 350°F. Grease a 9x13-inch baking dish with nonstick cooking spray.
Add the bacon to a cold nonstick skillet and cook on medium heat until some of the fat has rendered, but the bacon is not fully crisp. Set the bacon aside. Leave the bacon fat in the pan.
8 bacon slices
To the pan with the bacon fat, add the onions and cook until softened, about 5-7 minutes.
1 sweet onion
Add the onions, pork and beans, Worcestershire sauce, brown sugar, dry mustard, and molasses to the greased baking dish. Stir until combined.
60 ounces pork and beans in tomato sauce, 1½ teaspoons Worcestershire sauce, ⅓ cup brown sugar, 1 teaspoon dry mustard powder, ½ cup unsulphured molasses
Arrange the bacon pieces over the beans. Bake, uncovered, for 45 minutes or until the sauce is bubbly and the bacon is crisp.