In 3-quart rectangular baking dish, combine melted butter and olive oil. Whisk in balsamic vinegar, white wine, brown sugar, Herbs & Beef seasoning, salt, and pepper. Set aside.
Do not cut the ends off of the onions, but remove the papery skins. Cut onions in half from stem to root end.
Place onions in baking dish, cut sides up. Cover loosely with foil and bake for 30 minutes.
Remove foil. Using tongs, carefully turn onions over to cut sides down. Bake, uncovered, for 20 to 25 minutes longer or until onions are tender and balsamic mixture is thickened and caramelized. Serve cut sides up.