In the bowl of your electric mixer (or with a hand mixer), beat the butter and sugar until light and fluffy (about 3 minutes). Add the eggs and vanilla extract and beat until combined. Mix in your food dye, if using. Add the salt and baking soda and beat to combine. Add the flour and beat until you have a smooth dough. Divide the dough in half and wrap each half in plastic wrap. Refrigerate for at least one hour, preferably overnight.