Preheat oven to 350°F.
In a large mixing bowl, combine the zero-calorie sweetener, applesauce, and butter substitute. Mix with a rubber spatula until smooth.
Separately, whisk the egg until smooth and mix in. It’s ok if the mixture looks broken at this point, it actually isn’t.
Then add the vanilla, baking soda, and salt, followed by the flour and the chocolate chips. Use a rubber spatula to gently fold and make the dough.
Allow the dough to rest in the refrigerator for about 5-10 minutes so it can firm up slightly.
Scoop the cookies onto a parchment-lined sheet tray, about 2 tbsp of dough per cookie. You can roll them into perfect balls if you wish.
Bake the cookies for 11- 15 minutes until the edges are lightly golden and the top changes from shiny to matte. Be careful not to overbake because they will dry out. (Note: Some zero-calorie sweeteners prevent the cookies from turning golden brown. You can lightly spray them with cooking spray towards the end of the bake time and return them to the oven, which will help them become more golden brown and crispy on the outside).
After baking, allow them to rest on the pan for a few minutes to set before transferring to a plate or cooling rack.