Separate the egg yolks from the whites. Whip the egg whites until they reach a light, foamy texture.
In a separate bowl, stir the water and sugar together until the sugar dissolves, then pour this over the beaten egg whites.
Add all the remaining ingredients except the apples and blend well with a hand mixer.
Line your cake or pie pan with parchment paper. Arrange the sliced apples over the bottom and pour the batter on top.
Bake at 356°F (180°C) for about 50 minutes.
Let the pie cool slightly, then turn it upside down and serve.
Notes
Firm, tart apples hold their shape best after the flip. Let the pie cool slightly before inverting so the apple layer sets on top. Store covered at room temperature for up to 2 days, or refrigerate for up to 4.