Cut pork tenderloin crosswise into four even pieces. Place one pork piece between two sheets of plastic wrap. Pound lightly with the flat side of a meat mallet, working from the center to edges until about 1/4 inch thick. Remove and discard plastic wrap. Repeat with remaining pork pieces.
Stir together the flour, seasoned salt, onion powder, garlic powder, and black pepper in a shallow bowl. Dip pork pieces into the flour mixture, turning to coat evenly. Heat oil over medium heat in a very large skillet. Cook pork pieces in hot oil for 8 to 10 minutes or until no longer pink and juices run clear, turning once. (If all the pork pieces won't fit in the skillet, cook in two batches, adding additional oil if necessary.)
Serve pork on buns with a tablespoon of Chipotle Ketchup, lettuce, tomato, and onion.
[Cleaning tip: Once the stove top is cool, wipe up any oil splatters with Clorox(R) Disinfecting Wipes*. Rinse hands once complete.]
For Chipotle Ketchup: Combine ketchup, chipotle peppers, and vinegar in a small bowl. Makes 1/2 cup.