Heat oven to 400ºF. Heat two 9 in. pie pans or cake tins in the oven. Beat eggs, flour, milk and salt for 1 minute on medium speed with an electric beater. Remove pans from oven. Place 2 tbsps butter in each and rotate to cover well. Arrange apple slices in each pan, pour batter over. Mix cinnamon and sugar. Sprinkle over batter.
Bake uncovered until puffed and brown for about 20 – 25 minutes. Serve hot, with cream or vanilla sauce.