1. Spray a nonstick 10- by 15-inch baking sheet with cooking spray. In a bowl, whisk mayonnaise and milk. In another bowl, mix bread crumbs, dill, salt, and lemon pepper.
2. Dip each piece of salmon into mayonnaise mixture, turning to coat, then roll in bread-crumb mixture, turning to coat. Place pieces slightly apart on baking sheet and spray lightly with cooking spray.
3. Bake on the top rack of a 475° oven until surface is browned and salmon is opaque but still moist-looking in the center (cut to test), 12 to 14 minutes.