Soften butter and cream with sugarless sugar, with hand mixer for 2 minutes.
Beat in egg for another minute. Add vanilla and mix in.
Add flour of choice and baking soda, mix with beater until incorporated, scraping down bowl with spatula, as needed.
Cover and chill dough for 2 hours. When chilled, roll out to about 1/4" thickness and use cookie cutters to create desired shapes.
Using flat spatula, transfer cut-outs to baking sheet, spaced an inch apart, with silicone baking sheet or parchment paper.
Bake for 12 to 15 minutes or until turning lightly golden brown.
Remove from oven, and let cool before icing and decorating.
For icing:
Add sugarless sugar, egg and cream of tartar to bowl and use hand mixer to combine, until smooth for 2 to 3 minutes. If needed, ad a bit of water to thin down. Decorate as desired.