- Preheat oven to 350F (175C). Grease and flour a 9-inch round cake pan. 
- In a large bowl, whisk together gluten-free flour, cocoa powder, sugar, baking powder, baking soda, and salt. 
- In a separate bowl, combine buttermilk, oil, eggs, and vanilla extract. 
- Add the wet ingredients to the dry ingredients and mix until just combined. Be careful not to overmix. 
- Gradually add the boiling water to the batter and mix until smooth. The batter will be thin. 
- Pour batter into the prepared cake pan. 
- Bake for 30-35 minutes, or until a toothpick inserted into the center comes out with moist crumbs. 
- Let cake cool in the pan for 10 minutes before inverting it onto a wire rack to cool completely. 
- Once cooled, frost with chocolate frosting, if desired. 
- Optional Tips: For a richer chocolate flavor, substitute brewed coffee for the boiling water. If buttermilk is unavailable, substitute with regular milk mixed with 1 tablespoon of lemon juice or white vinegar, letting it sit for 5 minutes to curdle slightly. Ensure your gluten-free flour blend contains xanthan gum; if not, add teaspoon of xanthan gum to the dry ingredients.