Preheat oven to 350°F and line two baking sheets with parchment paper.
In a medium bowl, combine flour, salt, baking powder, and baking soda. Set aside.
In the bowl of a standing mixer with the paddle attachment or a handheld mixer, combine butter and sugar, mixing until light and fluffy.
Add in the egg and vanilla extract, and mix until combined and light in colour.
Mix in the dry ingredients until combined. Do not over-mix!
Use a cookie scoop or a spoon, scoop 1.5 tablespoon sized balls onto the baking sheets. Be sure to leave at least 4-5 inches between each ball of dough, as the cookies will spread out. If you'd like to roll the dough in sugar before baking, pour a little bit of sugar into a small bowl and roll the dough in it before placing it on the tray.
Bake one tray at a time for 8-11 minutes, until edges look set. The middles will look soft.
Let the cookies cool on the baking sheets for 10 minutes, then transfer to a cooling rack to cool completely. Enjoy!
Notes
FLOUR: It is very important that you measure your flour properly! The right way to measure your flour is to weigh it, or use the scoop and level method.EGG REPLACER: To make these vegan, replace the egg with one flax egg.