Line a 10 in round cake tin with parchment paper and set aside.
Using a mixer, whisk together the eggs and xylitol until light.
Add the almond meal, protein powder, coconut flour, baking powder, zest and juice of lemon and sour cream. Beat or fold by hand until the batter is smooth.
Transfer the batter to the prepared cake tin. Sprinkle the berries over top and gently press into the batter without letting them get covered.
Bake for 45 to 50 minutes until golden and cooked through.
Remove from oven and cool slightly before removing the tin.
Topping
Add butter and xylitol to a pan and cook until dissolved.
Add berries and cook until it reaches a sauce consistency, about 3 – 5 minutes.