CONGRATULATIONS on your fattie, and thanks for sharing, sure looks good from here! Here's my unasked for 2 cents, stop reading if you like - I usually like pre-cooking veggies first, depending on the situation. I almost always prefer the intense rich flavor of caramelized (to light golden or dark brown, depending) onions unless I'm eating a burger (or on a burger-mmm, caramelized onions & blue cheese). Same with mushrooms- they contain a LOT of water so I will often at least "sweat" them, or saute them more if I want to concentrate the flavor (if I hear "umami" one more time on foodtv I will scream...!) When I used fresh tomatoes in a fattie recently, I sliced them about 3/8" thick and "pan roasted" them - basically just let them sit over a fairly low flame (I had a little bacon fat in the pan already, so they weren't "frying" or sticking-a non stick pan would work too). Basically, I sweated a bit of the moisture out but not so much as to lose much texture or much volume. Worked really well in the fatties, and the flavor, again, was intensified. My daughter stole a slice out of the pan and couldn't believe how much flavor had concentrated -- almost like a marinara strength in flavor. They held up well in the fattie. and don't forget to stick a head of garlic in every time you smoke!