Preheat oven to 320F. Grease the bottom of 1-9" round pan and line with parchment paper. Do not grease the sides.
In a medium bowl, sift twice the cake flour (150g) and baking powder (1.5 teaspoon) and mix to fully blend.
In a large bowl (or a bowl of a standing mixer) whip the eggs (4) and sugar (200g) for 5-7 minutes until triple in volume, thick, and light in color.
Sift half of the flour mixture over the egg mixture, then use a rubber spatula to fold the flour in. Continue with the second half.
Add 1/3 of the sponge batter into the cream cheese custard and mix it in to thin the custard.
Fold the rest of the sponge batter into the cream cheese batter.
Pour the batter into the prepared pan. Place it over a large cookie sheet and bake over the middle rack for 40-50 minutes. Once the cake has a golden dry top but a the center jiggles, turn the oven off and let the cake cool in the oven for about 2-3 hours
Run a knife between the cake and the pan to release the cake from the pan.