Preheat the oven to 375˚F. Line a few sheet trays with parchment paper. set them aside for later.
Add the flour, baking soda, and salt to a bowl. Mix the ingredients with a whisk until they are evenly distributed.
In a separate bowl, cream the butter and sugar together until they turn light and fluffy. Then mix in the egg and vanilla extract until combined. Add in the buttermilk and mix.
Pour in the flour mixture then mix until all of the dry ingredients have been combined and a dough has formed. Cover the dough with plastic wrap and refrigerate for 30 minutes.
Scoop cookie dough balls about 2 tablespoons in size and place them onto the prepared sheet trays, spacing them about 2 1/2 inches apart. Bake them in the oven for 10-12 minutes. The edges should be set and the the center should still be soft.
Remove them from the oven and give the tray a firm bang on the table to release any air. This will help them flatten. Allow them to cook on the trays for about 5 minutes then transfer them to a wire rack to cool completely.