1. In a stand mixer, beat the cream cheese and butter on medium speed until combined and smooth. Add in the sugar and mix on medium speed for 5 minutes until fluffy.
2. Add in the egg, vanilla, zest, lemon juice, cornstarch, baking soda, and salt. Mix for 1 minute until combined, scraping the sides of the bowl as needed. Turn the mixer to low and add in the flour, mixing until just combined.
3. Cover the dough and refrigerate for at least 2 hours or longer. Once refrigerated, preheat oven to 350°F. Line a baking sheet with Silpat or parchment.
4. Remove the dough from the refrigerator and using a medium cookie scoop, scoop out balls of dough. Roll the dough into balls and place on the cookie sheet 2 inches apart.
5. Bake for 8-10 minutes or until the the bottoms just begin to turn golden. No more than 10 minutes. Transfer the cookies to a wire rack to cool completely.
6. Icing: Whisk together the powdered sugar, heavy cream, and zest until smooth. Dip the tops of the cookies into the icing, and place back on the wired rack to set.