In A Large Skillet, Combine The First Five Ingredients; Bring To A Boil. Add Salmon. Reduce Heat; Cover And Simmer For 15-20 Minutes Or Until Fish Flakes Easily With A Fork. Meanwhile, In A Saucepan, Saute Onion In Butter Until Tender. Stir In Flour, Dill, Salt And Pepper Until Blended; Gradually Add Milk. Bring To A Boil; Cook And Stir For 2 Minutes Or Until Thickened. Serve With The Salmon.