
Cut tenderloin crosswise into four equal pieces. Butterfly each piece by cutting about halfway into the thickness of the meat, then slicing partway into each side to create flaps. Spread open each piece of pork. Place pork between sheets of plastic wrap. Using the flat side of a meat mallet, pound pork to ¼ inch thick; season with salt and pepper.
Whisk together eggs, Dijon, and garlic powder in a shallow dish. Place cracker crumbs in another shallow dish.
Heat ¼ inch oil in a sauté pan over medium-high to 350–360°.
Dip pork in egg mixture, letting excess drip off. Dredge pork in cracker crumbs, pressing to adhere. Fry pork in oil, turning once, until meat is golden brown, 2–4 minutes per side.
Serve tenderloins on rolls with pickles, yellow mustard, and onion.