The BPT is a popular sandwich from the Midwest (claimed by either Iowa or Indiana, depending on who you ask).
It’s a pretty straightforward construction. For the tenderloin: cut about 1/4# of pork tenderloin, butterfly it, pound it out to about 1/4" thick, standard 3 part breading (seasoned flour, egg, panko bread crumbs), and shallow fry a couple minutes per side. For the sandwich: soft bun, mayo, mustard, iceberg, pickles, tomatoes, onion.
Typically, the BPT should be several times larger than the bun than reasonably makes sense. This one is on the small side.