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Firefly Jar Cake

Firefly Jar Cake

This Firefly Jar Cake is a stunning dessert designed to look like a glowing mason jar at night, featuring a dark frosting base with UV-reactive yellow frosting fireflies that glow under blacklight. A magical cake perfect for special occasions!
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Prep Time 40 minutes
Cook Time 30 minutes
Total Time 1 hour 10 minutes
Course Dessert
Cuisine American
Servings 12 slices
Calories 460 kcal

Equipment

Ingredients
  

  • 2 1/2 cups all-purpose flour
  • 3/4 cup unsweetened cocoa powder dark or black cocoa for deep color
  • 2 tsp baking soda
  • 1 tsp baking powder
  • 1/2 tsp salt
  • 1 cup unsalted butter softened
  • 1 3/4 cups granulated sugar
  • 3 large eggs
  • 1 tbsp vanilla extract
  • 1 cup buttermilk
  • 1/2 cup hot coffee enhances chocolate flavor
  • 3 cups buttercream frosting divided
  • 1 tbsp black gel food coloring for night sky effect
  • 1/2 cup tonic water for UV-reactive glow
  • 1/4 tsp vitamin B2 powder optional, enhances glow
  • 1 tbsp yellow gel food coloring for fireflies

Instructions
 

  • Preheat the oven to 350°F (175°C) and grease two 8-inch cake pans.
  • In a mixing bowl, whisk together the flour, cocoa powder, baking soda, baking powder, and salt. Set aside.
  • In another bowl, beat the butter and sugar with an electric mixer until light and fluffy.
  • Add the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.
  • Gradually add the dry ingredients, alternating with buttermilk and hot coffee, mixing until just combined.
  • Divide the batter evenly between the prepared cake pans and smooth the tops.
  • Bake for 28-30 minutes, or until a toothpick inserted into the center comes out clean.
  • Let the cakes cool in the pans for 10 minutes, then transfer to a cooling rack to cool completely.
  • Tint half of the buttercream frosting black using the black gel food coloring and set aside.
  • For the firefly frosting, mix the tonic water with the remaining buttercream and tint it yellow. Add vitamin B2 powder for extra glow.
  • Frost the entire cake with the black buttercream to create a night sky effect.
  • Using a piping bag, pipe small dots of the yellow UV-reactive frosting onto the cake to resemble glowing fireflies.
  • Chill the cake for 30 minutes before serving. Display under a blacklight to reveal the glowing fireflies!

Notes

  • Storage: Store in the refrigerator for up to 5 days. Bring to room temperature before serving.
  • UV Effect: Tonic water and vitamin B2 enhance the glow under blacklight. The stronger the UV light, the brighter the effect.
  • Extra Decoration: Add edible glitter or neon-colored stars to enhance the nighttime scene.

Nutrition

Serving: 1sliceCalories: 460kcalCarbohydrates: 60gProtein: 5gFat: 22gSaturated Fat: 14gPolyunsaturated Fat: 1gMonounsaturated Fat: 5gCholesterol: 90mgSodium: 260mgPotassium: 120mgFiber: 3gSugar: 50gVitamin A: 600IUCalcium: 80mgIron: 2mg
Keyword Blacklight Cake, Firefly Jar Cake, Glow in the Dark Cake, Mason Jar Cake, UV-Reactive Dessert
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