Preheat your air fryer to 400°F.
Scrub the russet potato clean and slice it into thin matchsticks.
In a bowl, toss the potato sticks with olive oil, half the sea salt, and half the garlic powder.
Place the potatoes in the air fryer basket and cook for 18 minutes until golden and crispy, shaking the basket halfway through.
In a separate mixing bowl, combine the ground beef, egg white, remaining sea salt, black pepper, and remaining garlic powder.
Form the beef mixture into one thick patty, pressing a small indent into the center with your thumb for even cooking.
Heat a non-stick skillet over medium-high heat and sear the patty for 5 minutes per side until the internal temperature reaches 160°F.
Wash and pat dry the romaine lettuce leaves to use as a bun alternative.
Place the cooked patty inside the lettuce leaves and top with tomato slices, red onion, and a spread of Dijon mustard.
Serve the burger immediately alongside the hot crispy fries.