1. Preheat oven to 350. Generously butter 8-inch cake pan. 2. Sprinkle brown sugar and cinnamon over bottom of pan. 3. Peel and slice apples and arrange over sugar to cover bottom of pan. Dot with butter. 4. Beat eggs until light in color. Mix flour and baking powder and stir into eggs with the oil, salt and vanilla. Pour batter over apples and bake for 45 minutes until firm and lightly browned. 5. Invert pan on heatproof platter and gently shake out cake. Serve hot with whipped cream, slightly sweetened and with a little cinnamon added.