Preheat oven to 350F degrees.
Using a stand mixer or hand mixer, beat together butter, cream cheese, and sugar until completely smooth. Add in egg, vanilla, lemon zest, and salt. Continue to whisk until everything is incorporated.
Add in flour, 1/2 cup at a time, as you continue to beat the mixture. When all of the flour is added the mixture should be crumbly (see picture above).
Form dough into a disk, cover with plastic wrap, and refrigerate for 15 minutes.
Cut dough in half. Leave one half in the refrigerator while you roll out the other half on a cutting board. Your dough should be about 1/4 thick (see blog notes).
Cut your shapes and carefully move to a cookie sheet greased with cooking spray. Reform scraps, roll out, and continue to cut out cookies until you have 14-15. Repeat process with other half of the dough (or keep in the refrigerator to make another batch later). You should have 28-30 cookies total.
Bake cookies for 10-12 minutes, until they look dry on top. Let cool completely.