Preheat oven to 350F. Line a 15-in. x 10-in. x 1-in. baking pan with heavy-duty foil; grease lightly.

Place salmon skin side down on foil.

Sprinkle with lemon-pepper and onion salt. Top with onion and lemon. Dot with butter. Fold foil around salmon; seal tightly.

Bake at 350° for 20 minutes. Open foil carefully, allowing steam to escape. Broil 4-6 in. from the heat for 8-12 minutes or until the fish flakes easily with a fork.

Combine all ingredients together and blend until smooth. Serve with salmon.