In a mixing bowl, add the softened butter and vanilla extract.

Use an electric mixer on medium speed to cream the butter and vanilla together until smooth and fluffy.

Gradually add the powdered erythritol or powdered stevia to the mixture. Start with a smaller amount, then taste and adjust according to your desired level of sweetness.

Add a pinch of salt if desired. Salt can enhance the flavor of the buttercream and balance the sweetness.

Slowly incorporate the heavy cream or coconut cream into the mixture, a little at a time, until you achieve your preferred consistency. The cream helps make the buttercream smoother and more spreadable.

Continue mixing the buttercream on medium-high speed until it is light, creamy, and well combined.

Taste the buttercream and adjust sweetness or flavorings as needed.

Your keto buttercream is now ready to use! You can use it to frost cakes, cupcakes, or any other keto-friendly desserts. If you prefer a thicker buttercream, you can refrigerate it for a little while before using. Remember that the buttercream will firm up slightly in the fridge due to the butter content, so you may want to let it sit at room temperature for a few minutes before using if it becomes too firm.

Please note that erythritol and stevia are common sugar substitutes used in keto recipes because they have a minimal impact on blood sugar levels. If you prefer other sweeteners, be mindful of their carb content and adjust the quantities accordingly.