In a large skillet, place your thick-cut bacon slices and cook over medium heat for about 6-8 minutes, flipping occasionally. Transfer bacon to a plate lined with paper towels to drain excess fat.

In the same skillet, add sliced onions to the remaining bacon fat. Cook over low to medium heat for 15-20 minutes, stirring occasionally, until they achieve a rich, golden-brown color.

Slice the hamburger buns in half. Toast the cut sides in a separate skillet over medium heat for 2-3 minutes until lightly golden.

Spread a layer of BBQ sauce onto the bottom half of each bun. Layer crispy bacon followed by caramelized onions and drizzle additional BBQ sauce if desired before placing the top half of the bun.

Close the buns and cut each sandwich in half if desired. Serve immediately.