Preheat the oven to 375 °F. Line the bottom of a cake pan with parchment paper and lightly grease.
Sift together 1½ cups of flour, sugar, salt, and baking powder.
Cut in ½ cup of butter until the mixture is crumbly
Stir together the egg and cream.
Gently mix the cream into the flour mixture to form a soft dough.
Press into the prepared baking dish.
Cut the apples into thin slices. Create layers of overlapping apples in neat, uniform rows on the dough.
For the streusel, mix together the brown sugar, 2 tbsp flour, and cinnamon in a small bowl.
Crumble 2 tbsp of butter into the mixture. Sprinkle the crumble over the apples.
Bake in the preheated oven until the apples have softened and the topping has browned (approx. 25 minutes).
Cool the apple cake and serve.