Place skin side of salmon on ungreased foil (if salmon does not have skin, then grease foil). Spread with mustard. Combine sugar, chili powder, and lime zest and sprinkle over salmon. Pre-score salmon into serving size pieces by cutting almost all of the way through. Grill until done but do not overcook. You should be able to use a spatula to lift the serving pieces off the skin while the skin sticks to the foil. Serve with lime wedges.