Preparation

Make the red-eye onions

• In a large cast-iron skillet, melt the fat over high heat. Add the onions and cook, stirring, frequently for about 10 minutes (it’s OK if they burn a little on the edges). Meanwhile, in a measuring cup, combine the espresso and 3 Tbs. boiling water. Stir to combine, let sit for a few minutes, and then strain into a clean measuring cup. Once the onions are soft and slightly browned, stir the sugar into the pan, and then deglaze with the espresso and Worcestershire.
• Lower the heat, and cook until the liquid has evaporated, about 4 minutes. Set aside. The onions can be prepared up to 3 days in advance and stored in an airtight container in the refrigerator.

Make the sandwiches

• Position a rack in the center of the oven, and heat the oven to 375°F. Season the meat generously with salt and pepper.
• Put a cast-iron skillet over high heat. When hot, add the fat. When starting to smoke, sear the meat in batches, adding more fat as needed. Cook on both sides, stirring the meat occasionally, 3 to 4 minutes total. It’s OK if the steak separates into pieces, but you don’t want shreds or chopped meat. Transfer the meat and its cooking juices in batches to a plate.
• Place the rolls on two large rimmed baking sheets, and split them lengthwise, keeping them attached on one side so that they open like a book. Top one side of each roll with the cheeses. Place in the oven just long enough to melt the cheeses but not to toast the rolls, 5 to 7 minutes. Remove the rolls from the oven and distribute the meat evenly on the cheese side of the rolls. Top the bread side with the hot pepper spread and the onions. Fold the sandwiches together, and then slice and serve.