Preheat the oven to 180°C (356°F).
Place room temperature butter and cream cheese in a bowl and mix until smooth.
Add the sweetener and mix well, then add the eggs one at a time, mixing after each addition.
Sift in cake flour and baking powder, gently fold with a spatula.
Pour in the milk and mix until the batter is smooth and not lumpy.
Evenly distribute the batter into muffin molds.
Bake at 180°C (356°F) for 20 minutes.