01 - Preheat oven to 350°F. Grease a 9-inch round cake pan and line with parchment paper.
02 - Whisk together flour, baking powder, salt, cinnamon, and nutmeg in a large bowl.
03 - Add cold butter cubes and rub into flour mixture with fingertips until mixture resembles coarse breadcrumbs.
04 - Stir in 3/4 cup sugar and sliced apples, tossing to coat evenly.
05 - Beat eggs, milk, and vanilla extract together in a small bowl.
06 - Pour wet mixture into dry ingredients and fold gently until just combined. Do not overmix.
07 - Transfer batter to prepared pan and smooth top. Sprinkle with 2 tablespoons sugar.
08 - Bake for 45 to 50 minutes until golden and a skewer inserted in center comes out clean.
09 - Heat milk and cream in saucepan over medium heat until just simmering.
10 - Whisk egg yolks, sugar, and cornstarch in a bowl until pale and smooth.
11 - Gradually pour hot milk mixture into yolks while whisking constantly.
12 - Return mixture to saucepan and cook over low heat, stirring constantly until thickened. Do not boil.
13 - Remove from heat and stir in vanilla extract.
14 - Let cake cool slightly before serving warm slices with vanilla custard.