Brush buns with melted butter - broil several minutes until toasty & golden. Remove set aside.
Chop onion & peppers
Combine onion, peppers, flank steak & bison in large skillet & cook on med-high until fully browned
Once meat is thoroughly cooked - add entire bag of Velveeta shreds, 7-8 slices of provolone cheese & Velveeta slices.
Stir until all cheese has melted throughout meat.
Spoon onto prepared buns
Top with another slice of provolone cheese & allow to melt
Top with onion & onion ring