Preheat oven to 350 degrees F (175 degrees C). Line a 12-cup muffin tin with paper liners.
Whisk together gluten-free flour blend, sugar, cocoa powder baking soda, baking powder, and salt in a large bowl.
Mash banana in a bowl. Add cooled coffee, oil, almond milk, apple cider vinegar, and vanilla extract. Whisk until combined. Pour into flour mixture. Stir slowly until just combined; batter will be thick and gummy.
Ladle batter into the lined muffin tin, filling cups 2/3 full.
Bake in the preheated oven until a toothpick inserted in the center comes out clean, 18 to 20 minutes.
You can use a store-bought gluten-free flour blend or make your own. It is important to use a blend in order to make sure the cupcake will not be too dense (if you use only whole-grain flour) nor too gummy (if you use only white rice flour or starchy flours). I used a combination of 150 grams white rice flour, 150 grams corn starch, 100 grams almond meal, and 100 grams brown rice flour, all sifted together. This means my blend was 60% white flours (white rice and a starch) and 40% whole-grain/nut flours (almond and brown rice). You can experiment with bean flours, but the flavor of the bean may come through in the cooking.