Preheat oven to 350°F and line a muffin tin with 12 cupcake liners.
In a bowl, whisk flour, baking powder, salt, and cinnamon.
In a mixer, cream butter and sugar until light and fluffy (2–3 minutes).
Beat in eggs and vanilla extract.
Alternate adding dry ingredients and the coconut milk + coquito mixture until fully combined.
Divide batter evenly among liners.
Bake 18–20 minutes, or until a toothpick inserted comes out clean.
Cool completely on a wire rack before frosting.
For Rum Buttercream: Beat butter, add sugar, coquito, coconut milk, and vanilla. Pipe or spread over cooled cupcakes.
For Coconut Whipped Cream: Whip cream to soft peaks, add sugar, coquito, and vanilla. Whip to stiff peaks. Frost as desired.
Garnish and serve chilled or at room temperature.