These fluffy churro cupcakes capture the nostalgia of a fairground with tender cinnamon cake, hidden sugar-crunch layers, and a rich, cinnamon-spiced buttercream topping.
Preheat your oven to 350 F (175 C) and line a cupcake tin with paper liners to ensure the batter stays airy once mixed.
In a medium bowl, whisk together the sugar, cake flour, baking powder, baking soda, salt, and cinnamon until the mixture is an even tan color.
Add the butter to the dry ingredients and beat on high speed for three minutes until the mixture looks like light, sandy frosting.
In a separate small bowl, whisk the eggs, sour cream, and vanilla extract until the mixture is completely smooth.
Combine the egg mixture with the flour mixture, beating on medium speed just until the dry patches disappear.
Slowly pour in the whole milk while mixing on low speed until just combined, noting that a thin batter is expected.
Create the cinnamon sugar layers
Stir the 3 tablespoons of sugar and 4 teaspoons of cinnamon together in a small bowl until well blended.
Spoon a thin layer of batter into the bottom of each liner, then dust with a light veil of the cinnamon sugar mixture.
Add more batter until the liners are 1/4 full, add another thin layer of cinnamon sugar, and then top with more batter until the liners are exactly 1/2 full.
Bake and cool
Bake for 14 minutes, testing with a toothpick to ensure it comes out clean. If needed, add 2 minutes of bake time.
Remove the cupcakes from the tin immediately and transfer them to a wire rack to cool completely to prevent the bottoms from becoming gummy.
Whip the frosting and finish
Beat the butter on high speed for three minutes until it becomes pale, airy, and no longer appears glossy.
Gradually add the powdered sugar, mixing thoroughly between each addition until the buttercream is thick and holds soft ridges.
Mix in the cinnamon and salt for one more minute until the frosting is stiff enough for piping.
Pipe or spread the frosting onto the cooled cupcakes and finish with an optional sprinkle of cinnamon sugar for extra sparkle.
Notes
Cake Flour Tip: Use cake flour for the lightest crumb. If using all-purpose flour, replace 2 tablespoons of flour with 2 tablespoons of cornstarch to mimic the texture.Baking Science: Do not open the oven door during the first 10 minutes of baking to prevent the centers from collapsing before the structure is set.Storage Instructions: Store cupcakes in an airtight container at room temperature for up to 2 days. Avoid refrigeration as it can dry out the cake crumb.Crunch Maintenance: Keep the cupcakes away from humidity to prevent the internal cinnamon sugar layers from softening. A 5-second microwave pulse can help restore the bite.Nutrition information is estimated based on common ingredients and serving sizes and may vary.