Preheat your oven to 350°F (175°C) and line a muffin tin with cupcake liners.
In a mixing bowl, whisk together the gluten-free flour, cocoa powder, baking powder, baking soda, and salt.
In another bowl, combine the sugar, vegetable oil, eggs, and vanilla extract. Mix until smooth.
Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk. Mix until just combined.
Stir in the peppermint extract.
Divide the batter evenly among the cupcake liners, filling each about two-thirds full.
Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
Let the cupcakes cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.