Prepare hamburger patties by carefully forming ground beef.
Heat 2 medium pans over medium heat. In one, melt the butter.
In the other, add the bacon and cook it until it's nice and crispy.
While the bacon is cooking... to the pan with the butter, add the onions, salt and pepper, and reduce the heat to low.
Cook them for about 10 minutes, stirring often. Make sure to watch the heat - you do not want them to burn.
Cook for 2-3 minutes, and then add the raspberry preserves.
Reduce heat to low, and cook for another 10 minutes, stirring often.
Preheat grill on high heat.
Liberally salt both sides of the burger patties and then throw the burgers on the grill.
When they are halfway done cooking (about 5 minutes), flip them.
Cook them for a few more minutes and then add the cheese and bacon on top.
Once the cheese is nice and melty, place burger on the bottom of the bun and add the raspberry caramelized onions on top.