In a bowl, mix together flour, baking soda, and salt.
In a stand mixer or a second bowl, add butter and beat with the paddle attachment or an electric mixer till creamy, approximately 1 minute. Add sugar and beat till smooth, approximately 2 minutes. Add egg and continue to beat for 1 minute. Add sun butter and vanilla and beat till combined. Stop to scrape down sides of bowl as needed.
Add dry ingredients to wet and beat on low speed till combined. Cover dough, place in refrigerator, and chill for at least one hour and up to 1 to 2 days.
Preheat oven to 350 degrees F. Line two baking sheets with parchment paper or silicone baking mats.
Remove dough from refrigerator and use 1 tablespoon of dough per ball. Place balls on baking sheets 2 inches apart.
Using a fork, make a criss-cross indentation on top of each and flatten slightly.
Bake 10 to 12 minutes until they are lightly browned.
Cool before eating.