Heat a medium deep pan over medium heat and melt the butter. Add the flour until smooth and bubbly. Add the milk, salt and cayenne pepper. Continue stirring until sauce thickens about 3 minutes then remove from heat.
Add the cheese and stir until melted then stir in the egg yolks.
In a medium bowl, using a handheld mixer, beat egg whites and cream of tartar until peaks form. Add the egg whites with the cheese mixture and gently stir to incorporate. Fill the souffle dishes about ¾ full and place them on a baking dish. Bake for 25 minutes if using large souffle dishes and about 15 minutes with smaller dishes. Serve