Preheat the air fryer to 360°F (182°C).
Lightly coat a 6×2-inch cake pan with cooking spray, covering the bottom and sides.
In a large bowl, combine 4 ounces fully cooked, crumbled breakfast sausage; 4 large eggs, slightly beaten; 1/2 cup shredded cheddar–Monterey Jack cheese blend; 2 tablespoons diced red bell pepper; 1 chopped green onion; and 1 pinch cayenne pepper. Stir until evenly mixed.
Pour the egg mixture into the prepared cake pan and spread it evenly.
Place the cake pan in the preheated air fryer and cook at 360°F for 18–20 minutes, or until the frittata is set in the center and lightly golden on top (a toothpick inserted in the center should come out mostly clean and the frittata should not jiggle).
Carefully remove the hot pan from the air fryer with oven mitts, let the frittata rest for 3–5 minutes, then slice and serve.