Minced onions burning on bagels

Hi there, 

I am in the process of starting up a new bagel business. I have finally moved into the kitchen and now have access to a 4 deck rotating oven. I have the recipe down and process, but the only thing holding me back at the moment are the onion toppings! 

I use dry minced onions. I have tried rehydrating them, cooking them normally, and spraying them down with water before they go in. I cook at 475 degrees and they always seem to burn. This has been driving me insane and cannot figure out how to get them to not burn. I have tried bagel boards but with this oven and just being me in the kitchen, it is not possible to do it all myself and cook volume, so I bake them on sheet pans. 

When I rehydrate the onions, after I boil them, they do not stick to the bagel at all. Does anyone have any recommendations on cooking bagels with onions? It would be greatly appreciated :) 

Thanks in advance!