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Grapefruit Poppy Seed Cake

A stunning three-layer citrus cake featuring two tender poppy seed layers and a striking pink grapefruit center layer, finished with a tangy grapefruit buttercream and fresh blueberries.
Print Recipe
Prep Time 45 minutes
Cook Time 35 minutes
Total Time 1 hour 20 minutes
Servings: 10 slices
Course: Cake, Dessert
Cuisine: American, Baking, Spring
Calories: 680
Ingredients Equipment Method Notes

Ingredients
  

Cake Batter
  • 3 cups all-purpose flour spooned and leveled
  • 2 tsp baking powder
  • 0.5 tsp baking soda
  • 1 tsp kosher salt
  • 1.75 cups granulated sugar
  • 2 tbsp ruby red grapefruit zest freshly grated
  • 1 cup unsalted butter softened to room temperature
  • 4 large eggs room temperature
  • 1 tsp pure vanilla extract
  • 1 cup buttermilk room temperature
  • 0.33 cup fresh ruby red grapefruit juice
  • 3 tbsp black poppy seeds
  • 1-2 drops pink gel food coloring optional, for middle layer
Grapefruit Buttercream Frosting
  • 1.5 cups unsalted butter softened to room temperature
  • 4-5 cups powdered sugar sifted
  • 2 tbsp fresh ruby red grapefruit juice reduced from 1/4 cup
  • 1 tsp freshly grated grapefruit zest
  • 0.5 tsp pure vanilla extract
  • 1 pinch salt
Garnish
  • 1 tsp black poppy seeds
  • 0.5 cup fresh blueberries

Equipment

  • Stand mixer or hand mixer
  • Three 8-inch round cake pans
  • Mixing bowls
  • Offset spatula

Method
 

  1. Preheat oven to 350°F (175°C). Grease and line three 8-inch round cake pans with parchment paper.
  2. In a stand mixer bowl, rub the grapefruit zest into the granulated sugar with your fingertips until fragrant and wet.
  3. Whisk together flour, baking powder, baking soda, and salt in a separate bowl.
  4. Beat softened butter into the zested sugar until light and fluffy. Add eggs one at a time, then vanilla extract.
  5. On low speed, alternate adding the dry ingredients in three parts with the buttermilk and grapefruit juice in two parts. Do not overmix.
  6. Divide batter. Move exactly 1/3 of the batter to a small bowl and gently fold in pink gel coloring. Fold the 3 tbsp of poppy seeds into the remaining 2/3 of the batter.
  7. Pour pink batter into one pan. Divide poppy seed batter between the remaining two pans. Bake for 25-30 minutes until a toothpick comes out clean.
  8. Cool cakes in pans for 10 minutes before turning out onto wire racks to cool completely.
  9. For the frosting, beat softened butter until pale. Gradually add powdered sugar. Add reduced grapefruit juice, zest, vanilla, and salt, whipping until fluffy.
  10. Assemble by placing a poppy seed layer down, spreading frosting, adding the pink layer, spreading frosting, and topping with the final poppy seed layer. Frost the entire outside, garnish with poppy seeds and blueberries.

Notes

To ensure vibrant flavor without a watery frosting, simmer 1/4 cup of grapefruit juice in a small saucepan until reduced by half, let it cool, and use 2 tablespoons of that reduction in the buttercream.