In a heavy saucepan combine the scalded milk, cornmeal, butter, sugar, salt, nutmeg, and cayenne. Bring the liquid to a simmer over moderately low heat, and simmer the mixture, stirring vigorously, for 5 minutes. Scrape the mixture into a large bowl and let it cool for 5 minutes.
In a bowl with an electric mixer, beat the egg yolks with the baking powder until the mixture is light and lemon colored and stir the mixture into the cornmeal mixture.
In a large bowl with the electric mixer beat the egg whites with the cream of tartar and a pinch of salt until they hold stiff peaks, stir 1/4 of them into the cornmeal mixture, and fold in the remaining whites gently, but thoroughly. Pour the batter into a well-buttered 1-quart souffle dish and bake it in a preheated moderate oven (350 degrees) for 40 minutes, or until the top is golden brown. Serve immediately.