I'd say pork loin and sone kind of paste rubbed in. Given there is an avocado in upper right corner, going to go with an annatto and/or chile based rub/paste.I just spent close to five minutes trying to figure out if the photo in the OP is pork or chicken, and how it was cooked.
Flat Iron Steak and Chuck Steak are different cuts here. They come from the same part of the cow, but a Flat Iron Steak is not the same, from my experience. People here sometimes call it "poor man's tenderloin/filet mignon." It is very tender. I love it.
I was pleasantly surprised how much I liked it, it was pre- marinated so I guess that would have altered it a fair bit. But even plainly seasoned before joining the other ingredients the flat iron was lovely.
I just spent close to five minutes trying to figure out if the photo in the OP is pork or chicken, and how it was cooked.
Flat iron steak first appeared here in the early 2000s. Kroger stores made it popular when they started to carry it in the mid 2000s.
It got popular in restaurants for a while, which ran the price up, but that fad passed, and now it is a relatively cheap cut, again. I always have some vacuum sealed in the freezer.
I've never used it for stewing. I always cook it like a good steak -- nice char on the outside, and medium rare inside. It is really tender, even though it is relatively lean.
Bavette steak also appeared around the same time which I believe for us is skirt but dont quote me on that.