Preheat the oven to 350˚F.
Lay parchment paper on cookie sheets.
Place butter and sugar in bowl of stand-up mixer and mix on low speed for a few minutes. Butter will soften. Set aside. If using orange zest, mix with sugar first.
In small bowl, beat eggs with whisk. Stir in vanilla and salt.
Add egg mixture to butter mixture. Mix until well blended.
Add flour one cup at a time to liquid mixture. Mix with stand mixer on low until dough forms.
Remove dough from bowl and place on clean, lightly floured counter. Knead lightly until it is uniform. Set dough aside.
Lightly flour counter and rolling pin with extra flour. Take a portion of dough and roll out to ⅜” thick. Dust flour as needed to ensure that dough does not stick to counter. Use cookie cutters to cut out cookies.
Transfer all cookies with spatula on baking sheets.
Bake for 9 to 11 minutes, or until the edges are just turning golden. If you prefer a crispier cookie, bake until lightly golden.
Allow cookies to cool completely before frosting.