Preheat oven to 350°F (175°C) and line a cupcake pan with paper liners.

In a medium bowl, whisk together flour, baking powder, baking soda, salt, and cinnamon. Set aside.

In a large bowl, cream the butter and sugar until light and fluffy.

Beat in the eggs one at a time, then add the vanilla extract.

Mix in the horchata and sour cream until just combined.

Gradually add in the dry ingredients, mixing until smooth and well incorporated.

Divide batter evenly among cupcake liners, filling each about 2/3 full.

Bake for 18–20 minutes or until a toothpick inserted in the center comes out clean. Let cool completely.

For the frosting, beat butter until creamy. Add powdered sugar, cinnamon, vanilla, and horchata. Beat until smooth and fluffy.

Frost cooled cupcakes using a piping bag or spatula. Sprinkle with extra cinnamon if desired.