Preheat the grill on medium to high heat setting, slice the onions into 1/2 to 3/4 inch thick slices, form the ground beef into 4 - 4 ounce patties, rinse and dry the arugula, measure the cheese, set everything aside.

Make the sauce: mix the yogurt, dijon mustard, apple cider vinegar, sea salt, hot sauce, and honey together and set it aside.

Reduce the heat on the grill to medium. Season the burgers with salt and pepper, brush the balsamic vinegar and olive oil over the onions.

Place the burgers and onions on the grill. Cook the burgers and onions for about 5 to 6 minutes and flip them over, cook for five minutes longer or until the burgers reach your desired doneness. At this point, the onions should be cooked too (they will be soft and slightly browned on the outside).

Place the blue cheese on top of the burgers just before removing them from the grill and close the lid until it begins to melt. Remove the burgers from the grill and place them on a roll or a slice of bread and continue to assemble the burger by adding the onion, sauce and last the arugula. Serve your burgers with a side of the sauce.