Preheat oven to 325 degrees.
Use mixer fit with paddle attachment to beat butter, cream cheese, and sugar until very smooth and fluffy, about 4 minutes.
Mix in lemon juice and zest until well combined.
Add egg yolk and mix until just combined.
In a small bowl, stir together flour and salt. Gradually beat into butter mixture, about a 1/2 cup at a time, until well incorporated. Scrape down sides as needed.
Place dough into cookie press and squeeze onto cookie sheet, about 1 inch apart.
Bake until just golden, about 12-13 minutes. Remove from oven and let cookies cool completely before decorating.