Cook the bacon in a skillet until it's brown and crispy. Transfer to a paper towel and crumble into small pieces.
Season beef with salt and pepper and divide into 8 equal portions, then shape into patties. Use your thumb to make an indentation in 4 of the patties. Divide bacon among the 4 dented patties. Top each patty with the remaining 4 patties and press the edges together to seal.
Preheat a griddle or pan to medium-high heat. Cook burgers until browned on both sides – about 4 minutes for medium-rare, 6 minutes for medium and 8 for well done.
Meanwhile, melt the cheddar cheese in a small saucepan over medium heat. Once the cheese is melted, add Ken's Chunky Blue Cheese Dressing and whisk to combine. Keep warm. Divide the patties among the rolls, pour warmed cheese sauce over burgers, and top with tomato, lettuce and red onion.