In a skillet over medium heat, melt the butter for the marmalade. Add the onions to the pan and stir to coat with the butter. Cook the onions for 15-20 minutes or until they are soft and tender. Add the sugar, vinegar, and salt to the onions and stir to combine. Let simmer for another 5 minutes. Transfer the mixture to a bowl and keep warm.
Meanwhile, in a large bowl combine the ground chuck, Worcestershire and garlic powder. Shape into 4 large balls. Press a indent into the center of each ball and fill with blue cheese crumbles. Shape into a patty around the cheese so that it is completely enclosed and patty is about ½ inch thick. Grill burgers over medium heat for about 5 minutes per side or until desired doneness. Spread a thin layer of mayo on each bun, top with lettuce, burger and red onion marmalade. Serve and enjoy!