A whole sweet onion is cored, then filled with a beef bouillon cube and butter before being wrapped in foil and grilled. The butter and beef flavoring combine with the sweet onion for a surprisingly delectable side dish. A whole sweet onion is cored, then filled with a beef bouillon cube and butter before being wrapped in foil and grilled. The butter and beef flavoring combine with the sweet onion for a surprisingly delectable side dish. January 30, 2021 by Haley Lynn A whole sweet onion is cored, then filled with a beef bouillon cube and butter before being wrapped in foil and grilled. The butter and beef flavoring combine with the sweet onion for a surprisingly delectable side dish.