Preheat the oven to 360°F (180°C) and prepare a lightly greased baking pan or a couple of 12-cup muffin pans. Get the ingredients ready.
In a large bowl, using an electric mixer, mix the eggs and erythritol for 3 to 4 minutes. You want the mixture to become foamy.
Add oil, sifted flours, and baking powder. Mix on medium-low until well incorporated.
Put the batter into a lightly greased baking or muffin pan (do not use paper cups no matter what the picture shows.
Cheesecake blueberry layer
In a large bowl, using an electric mixer, mix the eggs and erythritol for 3 to 4 minutes. You want a foamy mixture as before.
Continue to mix on medium-high, and add cream cheese, vanilla protein powder, vanilla extract, and sour cream. Mix until there are no lumps left in the batter.
Pour the batter onto the sponge cake layer and sprinkle with blueberries.
Bake for 40 or 45 minutes. Baking time does depend on the size of the dish, so make sure that the toothpicks inserted in the middle comes out clean.
Enjoy while still warm or when cooled and chilled in the fridge.