Grease the pan with butter. Put the dough in the pan and stretch it a little to the edges until it covers the walls of the tray remain little beyond. Remove the dough, which is left outside the tray and twist (to be used for decoration). Pierce the dough with a fork. Cut the apples into thin pieces and put them in water or pour them with lemon juice to not turn black. To prepare the cream you need a small saucepan, where you have to boil the milk with lemon peel and cinnamon. Mix flour and sugar, then add the egg yolks. Mix them until obtaining a smooth mixture. Pour it into the pan with the milk and cook for 5-6 minutes without stopping mixing. Allow to cool a bit, remove the zest and pour into pan on the dough. Arrange the sliced ​​apples in a circle until it covers the entire cream. Put it in a preheated oven at 200 ° C and bake for 20 minutes until the start to blush on top. Remove from the oven, sprinkle with powdered sugar, put the ends twisted dough again and returned to the oven for 10 minutes. Then removed and allowed to cool before serving.