Preheat your oven to 375 degrees. Melt the butter in the microwave and put it in the fridge to cool. Mix the cake mix, melted butter, eggs, lemon zest, vanilla, and salt in a mixing bowl--handmix at first and then if you still have lumps of cake mix, you can use an electric beat on low to get the rest out. It will gather into a thick dough.
Sift the cornstarch and powdered sugar together in a small bowl. Line a cookie sheet with parchment paper and roll your cookie dough into 1 inch balls. Roll the ball into the sugar mixture and place it on the pan. Bake for 10 minutes.
Best eaten after completely cooled or refrigerated.
Recipe by Honeybear Lane at https://www.honeybearlane.com/2013/12/red-velvet-cake-mix-cookies.html