Preheat air fryer to 400°F. Toss diced potatoes with olive oil, salt, and pepper. Air fry for 16–18 minutes, shaking halfway, until golden and crispy.

Heat a skillet over medium-low with a little olive oil. Add diced onions and cook 10–15 minutes, stirring occasionally, until soft and golden. Remove and set aside.

In the same skillet, increase heat to medium-high. Add ground beef, break it up, and press it into the pan to create crispy edges. Cook 5–7 minutes until browned. Season with salt and pepper. Drain excess fat if needed.

In a small bowl, whisk together mayo, ketchup, mustard, and Cajun seasoning until smooth.

Add crispy potatoes to bowls, top with beef, caramelized onions, and shredded cheese. Drizzle with special sauce and finish with lettuce and optional toppings.