Pat the crab meat dry with paper towels and check carefully for any shells.
In a mixing bowl, combine mayonnaise, Dijon mustard, Old Bay seasoning, and breadcrumbs.
Gently fold in the crab meat, red bell pepper, and green onions without overmixing.
Form the mixture into 4 patties about 3 inches wide and 3/4 inch thick, pressing firmly so they hold together.
Preheat the air fryer to 375°F for 3 minutes.
Spray the air fryer basket with nonstick cooking spray.
Place the crab cakes in the basket without touching and spray the tops lightly with oil.
Air fry at 375°F for 12 minutes until edges are golden brown and centers feel firm.
Squeeze fresh lemon juice over the crab cakes before serving.