Cast Iron Grilled Turkey Burger w/Grilled Onions & Cheese

Alright so not the first time I've posted about this and surely won't be the last. I'm still in search of the perfect Turkey Burger and won't stop until I find it.....or make it!:)

Unfortunately I can't give away my secrets so pictures are all that we can do.

Grilled onions if you forgot...

• 2 large onion sliced 1 inch thick
• Salt....Pepper...Teaspoon of olive oil
• With your hands toss all ingredients together and bake at 400 degrees for 40 minutes