Cook bacon. Crumble and set aside. Keep pan with bacon grease to use later for the bratwurst.
Meanwhile, prepare jalapeno mayo. Mix together the mayonnaise, diced jalapeno, garlic, and pinch of salt in a small bowl, to combine. For a smoother sauce, blend with a splash of liquid (water or lime juice work well) in a food processor.
Melt butter in a separate skillet over medium heat. Add sliced onions and cook until onions begin to brown. Add brown sugar and stir to combine. Continue cooking until onions begin to sizzle and sugar forms a light glaze. Remove from heat.
In the pan with bacon grease, cook bratwursts until fully cooked and heated through.
Serve Cheddarwurst on Martin’s Long Potato Rolls topped with onions, crumbled bacon, and jalapeno mayo.