1. Add 1 cup of white vinegar and 3 Tbsp of sugar to a medium bowl and stir until the sugar dissolves.
2. Chop ends off red onion and peel off the outer skin, then slice thin. Add the onion ring slices to the vinegar, cover and set aside to allow it to pickle while you prep the other ingredients and cook the burgers.
3. For the balsamic blueberry sauce: heat the Blueberry-Lime jam slowy in a little pan and mix with the balsamic vinegar, then let it simmer for 5 to 6 minutes, stirring occasionally.
4. Prep the Brie cheese by cutting into slices to place on the burgers.
5. Take a handful of beef and shape into palm-sized burger patties, creating a slight indentation in the middle. Season with salt and pepper.
6. Grill or pan fry your burgers for 4-6 minutes. Then flip, add the Brie, cover and cook for an additional 2-3 minutes until the cheese has melted.
7. Assemble the burgers onto sliced Kaiser rolls, topping with Balsamic Blueberry Sauce, pickled red onions, and arugula.