Pre-heat oven to 375F
In a stand mixer with the paddle attachment, mix butter and sugar until fluffy on medium speed for aprox 3-4 minutes.
Add egg yolks, vanilla and lemon oil, mix to combine.
Add flour and salt slowly using a spoon to scoop into the mixer on low speed.
Mix just to combine. Dough will be crumbly but will hold together when squeezed into a ball.