Preheat oven to 350 F. Butter a 10 to 11 inch springform pan or a pan with a removable bottom.
Peel the apples, remove the core, dice/slice them (not too thick), place them in a bowl and stir in a tablespoon or two of lemon juice (to prevent browning). Set aside until the batter is ready.
In a small bowl combine the flour, baking powder, and salt. In a large mixing bowl beat the butter, sugar, milk, vanilla extract, and cinnamon until pale and creamy/frothy. Beat in the eggs one at a time, mixing thoroughly before adding the next egg. Stir in the flour until combined but don't over-stir.Pour the apples into a colander and let them drain. Set aside a few pieces/slices to press into the top of the cake at the end. Stir the apple pieces into the batter and scoop the batter into the greased pan. Use the apple pieces you set aside and press them into the top of the batter. Bake for 40-55 minutes until a toothpick inserted into the center of the cake until comes out clean. Let the cake cool in the pan for 15 minutes and then remove it to let it cool completely.
If using the sugar cinnamon or apricot jam toppings (see blog post "Optional Toppings" for instructions), apply it while the cake is hot and then let the cake cool. If using powdered sugar, sprinkle it over the cake once it's cooled. Serve the cake on its own, with some whipped cream, homemade German Vanilla Sauce, or serve it with vanilla ice cream and/or a drizzle of homemade Caramel Sauce.Store the cooled cake in a cake saver or airtight container. This cake will be even more moist the next day. Will keep at room temperature for up to 3 days or can be refrigerated a little longer.