Preheat your oven or air fryer to 400°F (200°C).

Spread the frozen French fries evenly on a baking sheet or place them in the air fryer basket. Bake according to package instructions, usually around 20-25 minutes, or air fry until golden brown.

While the fries are cooking, melt 4 tablespoons of butter in a medium saucepan over medium heat. Whisk in 4 tablespoons of all-purpose flour and cook for about 2 minutes to form a smooth roux.

Slowly pour in 2 cups of milk while whisking continuously until the mixture thickens, about 3-5 minutes.

Once thickened, season with salt, ground black pepper, ranch seasoning powder, and cayenne pepper. Stir well and allow to cook for another minute.

Reduce the heat to low and stir in 2 cups of shredded white cheddar cheese until melted and smooth.

Serve the fries on a platter and drizzle with the creamy Cajun ranch cheese sauce. Add an extra sprinkle of cayenne pepper if desired.