Cut tops off onions; peel.
Remove centers, leaving a shell 1/2 to 3/4 inch thick.
Sprinkle insides of onions with salt.
Chop half the onion removed from centers; saute in 2 tablespoons butter or margarine.
Add parsley, marjoram, bread crumbs, pimiento, 1/2 teaspoon salt, and cheese.
Spoon into onion shells.
Brush with remaining butter or margarine.
Place in 1 1/2-quart casserole; cover.
Bake.at 400° for 45 to 50 minutes or until tender.