Preheat air fryer to 400 degrees F. Toss diced red potatoes with olive oil, salt, pepper, and preferred seasoning. Spread in a single layer without overlapping. Air fry for 16 to 18 minutes, shaking halfway, until golden and crispy.

While potatoes cook, heat a tablespoon of olive oil in a skillet over medium-low heat. Add diced onions and cook for 10 to 15 minutes, stirring occasionally, until deep golden and caramelized. Remove and set aside.

Raise skillet heat to medium-high. Add ground beef in loose chunks and press flat against the pan with a spatula. Hold for a few seconds. Cook for 5 to 7 minutes total, smashing and breaking up pieces, until browned with crispy caramelized edges. Season with salt and pepper. Drain excess fat.

In a small bowl, whisk together mayonnaise, ketchup, Dijon mustard, and Cajun seasoning until smooth. Adjust to taste.

Build each bowl with crispy potatoes as the base, then smashed beef, caramelized onions, and shredded cheese. Drizzle Cajun sauce generously over the top. Finish with pickles and lettuce. Serve immediately.