We have a great crop of onions this year and many they size of a softball. Hollow out the onion, use the onion parts scraped from the center plus spices to season the lean burger, stuff the onion, wrap it in bacon, dab it with BBQ sauce and smoke 'em mopping towards the end so the sauce grabs all the smoke after the bacon crisps. It is the best thing I've ever made on the smoker in 3 years!
If you want less onion, you can slice off the top and bottom then make a cut to center of onion from side, peel the layers (I like to double them) and stuff the centers of each forming a round 'bomb', wrap in bacon cook same way.