Preheat your oven to 350°F (175°C). Line a muffin tin with cupcake liners.
In a mixing bowl, whisk together the gluten-free flour, sugar, baking powder, and salt.
In another bowl, combine the melted butter, milk, eggs, and vanilla extract.
Pour the wet ingredients into the dry ingredients and mix until just combined.
Divide the batter evenly among the cupcake liners, filling each about ⅔ full.
Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
While the cupcakes are baking, mix together the sugar and ground cinnamon for the topping.
Once the cupcakes are done, let them cool for a few minutes, then dip the tops into the cinnamon sugar mixture.