Make the cinnamon sugar mixture for the rim: combine the cinnamon and sugar in a shallow bowl or dish.
Moisten the rim of a martini glass with water. Dip the rim of the martini glass into the cinnamon sugar mixture.
Fill a cocktail shaker with ice cubes. Pour the RumChata, vanilla vodka, pumpkin puree and pumpkin pie spice into the cocktail shaker. Shake vigorously for 15-20 seconds.
Strain the cocktail into the martini glass. Enjoy chilled.