Preheat the oven to 350 F. In a medium bowl, whisk together flour, salt, and baking soda. In a large bowl, mix together butter and sugar until fluffy. Add in egg and vanilla extract and mix until smooth.
Add in the flour mixture and mix until it is fully combined. Roll the cookie dough into balls and place onto a large ungreased baking sheet at least 2-inches apart. Bake for 10-12 minutes. Let cool completely.
In a large bowl, mix butter with powdered sugar and vanilla extract until combined. Add in the food coloring. Frost each cooled cookie and decorate with sprinkles.
