Preheat oven to 350°F and line two cupcake tins with liners for 18 cheesecakes. Add the shortbread cookies to a food processor and pulse until fine crumbs form. Add the melted butter and process again until fully combined.
Add the sour cream, eggs, lemon juice, and vanilla to the cream cheese mixture and beat until smooth. Measure 3-4 tablespoons of filling into the cupcake liners, leaving about ¼ inch of space from the top. Bake for 25 minutes, then turn off the oven and crack the oven door and leave the cheesecakes in for 1 additional hour to allow cheesecakes to set evenly.