Grate the red onion. Prepare outdoor grill, if using one.
Combine: bison, garlic, diced red onion, and peanut butter. Divide into 4 equal portions.
Place each piece between 2 slices of parchment paper or cling wrap. With a large spatula (or the bottom of a sauce pan,) push down uniformly on the meat so it is about 1/2 or 3/4 of an inch thick. Do not attempt to make the burger round. It should have jagged edges and an irregular shape. The irregular outer edges will cook up crisp, which is the beauty of this burger.
Place the burgers over hot, gray coals and grill, turning only once, until they reach an internal temperature of 140º.
Remove from heat, place a slice of Swiss cheese over each burger, and tent loosely with tin foil. The resting meat temperature will continue to climb to 145º, which is a perfect medium-rare burger!
While burgers rest for 5-7 minutes, place the halves of the buns on the side of the grill, or wrap them in foil and place on grill grates.
Top with Fak'n Bacon and dig in! Mmmmm!