To begin, add your milk and vinegar to a small bowl and stir them together. Set them aside so the milk will curdle making "buttermilk."
Now, preheat your oven to 350 and line two muffin pans with cupcake liners (for 15 cupcakes).
In a small mixing bowl, add your gluten-free flour, pumpkin pie spice, baking powder and salt and stir them together.
In a large mixing bowl, add your coconut oil and sugar and whisk them together. Then add your pumpkin puree, eggs and vanilla and whisk them together lightly. Finally, add your "buttermilk" and mix together till all is well combined.
Pour your dry ingredients into your wet ingredients and stir them together to make your cupcake batter.
Fill each liner about 3/4 way full with cupcake batter. Bake in the oven for 17-19 minutes, or till the tops of the cupcakes are springy to touch and a toothpick inserted comes out clean.
Let cool then top with your favorite frosting.
Devour!
Eat within two days. Or, store your cupcakes in the fridge and add the frosting on later and they will last a few days longer.