Preheat the oven to 350°F. Line two muffin pans with paper liners and set aside.
In a medium bowl, cream together the butter and 1 cup sugar until light and fluffy. Mix in the vanilla, eggs and pumpkin puree until fully incorporated.
In a separate bowl, mix together the flour, baking powder, baking soda, cream of tartar and salt until fully combined.
Slowly mix the dry ingredients into the wet ingredients until just combined. Add in the buttermilk and mix until smooth.
In a small bowl, mix together the 1/2 cup sugar with the cinnamon.
Scoop the batter evenly in the two muffin pans. Sprinkle the cinnamon sugar evenly on top of the batter.