Preheat the oven to 350° and line a cupcake pan with 12 liners.
In a large bowl, combine the buttermilk, avocado oil, eggs, and vanilla. Stir until well combined.
Add the matcha powder, baking soda, baking powder, cane sugar, and salt to the bowl, and stir until well combined and there are no matcha lumps.
Slowly add the whole wheat pastry flour in batches, stirring as you go. Don't overmix, but stir until the batter is well combined.
Fill each cupcake liner ⅔ full of the matcha cupcake batter. Bake for 15-16 minutes in the preheat oven, or until a toothpick inserted in the center of the cupcakes comes out clean. Allow to cool before frosting.
Make the frosting: In a small bowl, soften the room temperature butter by microwaving for about 8-10 seconds. Add to a mixing bowl, along with the powdered sugar, coconut milk and the coconut extract. Beat on medium high, until well combined and fluffy. Allow your cupcakes to cool, then frost.