Cut a 1/4-inch slice from top and bottom of each onion, reserving slices. Place onions in a Dutch oven; add water to cover. Bring to a boil. Reduce heat; cover, and simmer 20 minutes or until tender. Drain and cool.
Chop reserved onion slices; sauté in butter until tender. Add next 8 ingredients.
Scoop out center portion of each onion; discard. Fill each onion with olive mixture; sprinkle with paprika.
Place onions in a 13- x 9- x 2- inch baking dish. Cover and bake at 350° for 20 minutes. Uncover and bake an additional 5 minutes.