Slice the red onion into rounds that are ½ inch thick, being careful not to tear the onion rings apart. Remove off the table.

In a big bowl, mix together the bison, Worcestershire sauce, pepper, and salt. Carefully blend by mixing until well combined. Separate the mixture into four equal parts, each containing approximately 8 ounces. Roll into a ball (not too firmly), then flatten into a patty that is approximately one inch thick.

Simmer a big cast-iron skillet. Before coating the pan, add 2 tablespoons of butter and swirl it around. Brown the onion slices by cooking them for three minutes per side in a skillet over medium heat. Take it off the heat and put it aside.

Toss in the skillet with the other tablespoon of butter. After around 5 minutes of searing, the bison patties should be golden. Cook for another 3 to 4 minutes, flipping once, or until the burger's internal temperature reaches 130 to 135˚ (for medium-rare). Put the cheese on the burgers just before they're done cooking and cover to melt if you choose.

Quickly top the burgers with BBQ sauce, pickles, red onion rings that have been seared, and place them on toasted buns.