In a large mixing bowl, cream together the butter and cream cheese. Add the sugar and beat until the mixture is light and creamy. Add the egg and lemon zest and continue to beat until fully combined.

In a separate bowl, whisk together the flour and salt. Add to the butter mixture and mix until just combined, scraping the bowl along the way. Divide the dough into two parts, create disks, wrap in plastic wrap and chill in the refrigerator until ready for use, at least 30 minutes. This can be done a couple of days in advance.

Bring the dough to room temperature and place in a cookie press. Press the dough out onto an ungreased baking sheet. Bake for about 8-10 minutes or until just golden on the edges. Place on a rack to cool.