Parmesan Sourdough Cheeseburger

I got a little confused as to when to put on the onion. I grilled two thick slices of onion for part of the time as I was grilling the burgers. When the burgers were done enough for the cheese, I put the slices of sourdough on the grill, butter side down. I kind of forgot about the parmesan cheese, oops. My bread slices were huge, so I cut them in half before grilling and the burgers fit on half a slice easy. Building the whole thing - 1/2 slice of grilled sourdough, burger with melted cheese, grilled onion, tomato slice, mustard and other half of grilled bread. However it's stacked, this made a tasty meal along with the first fresh sweet corn of the year!