Soak herring overnight in water.
Remove skin and bones.
Cut into 1 in. (2.5-cm) pieces.
Place herring, onion, and beets in glass bowl.
Cover with dressing.
Marinate 4 to 5 hours or overnight.
Drain. (Keep liquid; it makes a very good salad dressing.) Arrange herring, onion, and beets on crisp lettuce leaf.