01 - Preheat your grill to medium-high heat, approximately 400°F.
02 - Heat vegetable oil in a skillet over medium heat. Add sliced onions and cook, stirring frequently, until softened and golden, about 8 minutes. Add drained sauerkraut and caraway seeds if using; stir and cook for an additional 3–4 minutes until heated through. Season with black pepper to taste.
03 - Place beef bratwursts on the grill and cook, turning occasionally, for 12–15 minutes until evenly browned and fully cooked. Internal temperature should reach 160°F.
04 - During the last 2 minutes of grilling, place buns cut-side down on the grill to toast lightly.
05 - Place a grilled bratwurst in each toasted bun. Top generously with the warm sauerkraut-onion mixture. Add mustard, ketchup, and pickles as desired. Serve immediately while hot.