Trim pork tenderloin of any fat and silver skin, and cut into 4 equal pieces. Place each piece between 2 sheets of plastic wrap or in a resealable plastic bag. Pound the cutlets using a meat mallet to 1/4-inch thickness, flattening each piece.
Combine flour, salt, onion powder, garlic powder, and pepper in a shallow dish. Whisk together buttermilk and egg in a second dish. Add panko breadcrumbs to a third dish.
Dry cutlets with paper towels, and dredge each in the flour mixture on both sides, shaking off any excess. Next dredge tenderloins in the egg-buttermilk mixture, shaking off the excess. Finally, turn cutlets in the bread crumb mixture, pressing down until completely coated. Transfer to a plate and let dry for at least 5 minutes.
Heat oil over medium heat in a 12-inch skillet to between 350 to 375 degrees F (175 to 190 degrees C). Place a couple of breaded cutlets in the skillet, making sure not to crowd, and fry on each side for about 3 minutes, shaking the pan occasionally until cutlets are deep golden brown and crisp. Transfer the cutlets to a wire rack to drain any excess oil. Repeat the procedure with the remaining cutlets.
Spread each roll with mayonnaise then add lettuce, pickle slices, and cutlets.
