1 lb uncured bratwurst
2 tbsp olive oil
1-12 oz bottle pilsner or other lager, divided
1 medium red onion, chopped
½ medium head of red cabbage, thinly sliced
1 medium red beet, peeled, coarsely grated
kosher salt and freshly ground pepper
½ cup apple cider vinegar
1 tbsp light brown sugar
¼ tsp ground allspice
Freshly grated horseradish, for serving
Prick bratwurst several times with a knife and place in a large skillet. Add oil and half of beer, then add water until liquid comes a little over half way up the sausages. Bring to a simmer over medium heat. Cook, turning once, until just barely cooked through, 12-15 minutes.
Increase heat to medium high; cook until liquid is evaporated, 5-10 minutes. Roll sausages to edge of skillet and add onion to center. Cool, turning sausages often and stirring onion occasionally, until sausages are browned and onion is soft, 5-8 minutes. Transfer sausages to a plate.
Add cabbage and beet to skillet; season with salt and pepper. Cook, stirring often, until cabbage is wilted, about 5 minutes. Add vinegar, brown sugar, allspice and remaining beer. Cover and cook until tender, 20-25 minutes. Serve sausages with cabbage mixture, topped with horseradish.