A smoky sausage on a toasted bun with mustard and onions is a high protein, quick cookout classic. This family-friendly sandwich is always a reliable, satisfying option at any barbecue.
Preheat the grill to medium-high heat (about 400°F) for 5 minutes to ensure the grates are hot.
Slice the onion thinly and set aside; melt the butter in a skillet over medium heat and sauté onions until golden and softened, about 6-8 minutes.
Place smoked sausage links on the grill perpendicular to grates for even browning. Grill for 6-8 minutes, turning occasionally until heated through with char marks.
Brush the hot dog buns lightly with remaining melted butter and toast them on the grill grates for about 1 minute, just until they are crisp and golden.
Assemble: Place each grilled sausage in a toasted bun, top with sautéed onions, and drizzle with yellow mustard. Serve immediately while hot.