I had this sandwich with my sister at a restaurant last month. It was a bitterly cold day, and we were starving. I couldn't decide what to order, and asked Sis what she was getting. "The brisket melt," she said, and I decided I had to have it too. The brisket was juicy and fall-apart tender, and served on challah with melted cheese, onions, and peppers. And I've been thinking of it ever since.
This version proved to be real easy. Instead of placing the brisket and vegetables in a roasting pan covered with foil like the recipe said, I used my cast iron braiser and its lid. Stick it all in the braiser, then in the oven, and come back in a few hours. Toast a roll, melt some cheese on it, top it with some sliced brisket and onions, and you're done. And really full.
I used Ina Garten's Brisket recipe, but downsized it for a 2½-pound brisket instead of the 6 or 7 pounds the recipe calls for. If you can't find brisket at your supermarket, ask the butcher. My only other deviation from the recipe was to use a can of tomato puree with some water instead of the tomato juice the recipe calls for, since I thought that was a weird choice of braising liquid and I didn't have any.