Heat an outdoor grill or a heavy cast-iron grill pan over medium-high heat until heavily smoking.

Brush both sides of the quartered red bell peppers, thick red onion slices, and Napa cabbage wedges generously with 2 tablespoons of the olive oil. Season evenly with the kosher salt and coarse black pepper.

Place the vegetables directly onto the hot grates. Grill undisturbed until deep, dark char marks form on the edges, while the centers just begin to soften, about 3 to 5 minutes total. (Do not overcook; the vegetables must retain their structural crunch to act as the taco filling).

Transfer the grilled vegetables to a clean prep board. Immediately drizzle the warm, charred Napa cabbage with the 2 tablespoons of white wine vinegar. (This acidic hit mimics the sharp tang of sauerkraut).

Using a sharp chef's knife, slice the raw bratwursts entirely in half lengthwise so they lay flat.

Brush both sides of the split brats with the remaining 1 tablespoon of olive oil.

Lay the split sausages cut-side down onto the hot grill grates. Sear aggressively until a deep, caramelized crust forms and the meat is cooked through, about 3 to 5 minutes per side. Transfer to a holding platter.

Briefly lay the flour tortillas directly onto the hot grill grates to toast and soften, turning them after just 10 to 15 seconds so they do not become brittle.

To assemble, slice the grilled onions and bell peppers into thin strips. Slice the vinegar-splashed cabbage into thin wedges.

Place a warm tortilla on a plate. Lay one heavily charred bratwurst half directly down the center. Top the meat heavily with the sliced vegetables and cabbage.

Garnish with a shower of fresh cilantro, a heavy squeeze of fresh lime juice, and a sharp drizzle of mustard before serving immediately.