Mix ground beef and minced onion and form into 4 patties. Gently press your thumb into the burgers about 1/3 inch in to keep them from turning too round when grilling.
Heat up grill and cook the burgers to your desire. Remove from heat, cover and keep warm.
Melt butter in saucepan over low heat. Whisk in flour and cook over low heat until it turns a golden brown whisking continuously approximately 2 minutes. Slowly whisk in beer and cheese alternating between the two and starting with the beer. Cook over low heat until all the cheese is melted.
Toast the pretzel buns, Top with burger, bacon, tomato and warm cheese.
Do not use any micro brews. I sometimes use a Corona or a Michelob Ultra.