3 packed tablespoons dark brown sugar
4 teaspoons prepared Chinese-style hot mustard or Dijon mustard
1 tablespoon soy sauce
1 teaspoon rice vinegar
2 salmon steaks (7- to 8-ounces each), ¾-inch thick)
Heat a grill to medium-high.
Combine brown sugar, mustard and soy sauce in medium bowl; whisk to blend. Transfer 1 tablespoon glaze to small bowl; mix in rice vinegar and set aside.
Brush 1 side of salmon steaks generously with half of glaze in the medium bowl. Place salmon steaks, glazed-side down, onto grill and cook until glaze is slightly charred, about 4 minutes. Brush top of salmon steaks with remaining glaze in medium bowl.
Carefully flip salmon over and grill until second side is slightly charred and salmon is just opaque in center, about 5 minutes longer. Transfer salmon to plates. Drizzle reserved glaze in small bowl over salmon and serve.