Cream together your butter, cream cheese, and sweetener with your electric mixer. Add in the eggs and vanilla and mix. Add in the rest of the dough ingredients and mix until well incorporated. (Don’t over mix though).
Spread the dough in the prepared cake pan. Drizzle melted butter over the cake and sprinkle with the powdered erythritol.
Bake for 28-30 minutes until the cake is barely golden and doesn’t look wet on top. (Don’t over bake the case; it loses the texture of the traditional butter cake.)
Store at room temperature for 2-3 days. This cake does store well in the fridge for a bit longer. You can also serve with fruit, whipped topping, or your favorite ice cream if you're not watching your carbs.