Wikipedia
A Rostbrätel is a marinated cutlet of pork butt, that's grilled over charcoal. It is, like Thuringian sausage (Rostbratwurst), a Thuringian specialty.
The label "Rostbrätel" is common in West Thuringia and South Thuringia.
For preparation, about an inch cut of pork butt cutlet (with or without bone) is pressed (tenderized) and marinated in salt, pepper, Thuringian spicy mustard, onions and beer for two to up to 24 hours. The beer should be a dark, strong, somewhat sweet kind, not a Pilsener, as this adds a bitter taste. In some recipes, garlic and Caraway Seed are added as further spices.
Cooking is done on a charcoal grill. The grates are greased with pork fat, bacon, oil, butter or cooking spray in order to prevent sticking. While the meat is gently cooked over light to medium heat, it is basted after every turn with the marinade or with beer, sprayed directly from a gently shaken bottle. This serves to improve the taste and prevents a drying of the meat on the cooking surface. Moreover, the cooking temperature is regulated by gently spraying beer directly on the charcoal; the rising steam helps to cook and flavour the meat.
It is served with caramelized onions and a good German beer.