Preheat your air fryer to 400°F (200°C). Toss diced red potatoes with olive oil, salt, and pepper until coated, then cook in air fryer for 16-18 minutes until golden.

While potatoes cook, heat a tablespoon of olive oil in a skillet over medium-low heat. Sauté diced onions for about 10-15 minutes until soft and golden, then remove from heat.

Increase the skillet's heat to medium-high. Add ground beef, break apart, and cook for 5-7 minutes until browned, seasoning with salt and pepper.

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

To assemble, layer crispy potatoes in serving bowls, top with ground beef, caramelized onions, cheese, drizzle sauce, and sprinkle with lettuce and optional toppings.