This stunning creation combines the zesty essence of oranges with the delicate crunch of poppyseeds, resulting in a moist and flavorful cake that is both visually appealing and satisfying to the palate.
For cake: Preheat oven to 350°F. Grease 2 6-inch, 8-inch and 10-inch cake pans with butter, and line pans with parchment paper rounds. Dust pans with flour.
Working in batches if necessary, combine flour, poppy seeds, sugar, baking powder and salt in the bowl of a stand mixer fitted with a paddle attachment. With the mixer running on low speed, add butter, 1 tablespoon at a time, until mixture resembles coarse meal. About 3 to 4 minutes. Add the milk, orange and vanilla and beat, scraping down the sides, as needed, until combined. Add eggs, one at a time, until fluffy, about 2 minutes.
Divide batter between prepared pans, filling each pan roughly halfway. Bake until a toothpick inserted into the center comes out clean, about 25 to 30 minutes for 6-inch, 35 to 40 minutes for 8-inch, and 55 minutes to 1 hour for 10-inch. Let cakes cool in pans for 10 minutes. Invert onto wire racks and let cool completely.
For buttercream and assembly: Meanwhile, working in batches if necessary, whisk egg whites and sugar together in a stand mixer bowl until combined. Bring a large pot filled with 1-inch water to a simmer over medium-low heat. Place bowl over simmering water,whisking frequently, until reaches 160°F, about 8 to 10 minutes. Remove from heat. Transfer bowl to the stand mixer fitted with a whip attachment. Whip on medium-high speed until stiff peaks form, and mixture reaches room temperature, about 17 to 20 minutes.
While the mixer is running, add butter, 1 tablespoon at a time, until a thick and fluffy buttercream forms. Add salt and vanilla, and beat until combined. Set aside.
Once cakes have cooled, create a flat surface by removing a 1/4-inch from the crown of the cakes with cake level. Transfer one 10-inch cake to a 12-inch cake drum. Place the 8-inch and 6-inch cakes on cardboard cake rounds.
Place the 10-inch cake on the turntable. Using an offset or straight spatula, spread roughly 1/2-inch of buttercream evenly over the top, right to the edge of the cake. Place the remaining 10-inch cake layer on top, pressing gently to adhere. Repeat with the 8-inch and 6-inch cakes.
Using an offset or straight spatula, spread a thin layer of buttercream on the top and sides of each layered cake. Refrigerate for at least 30 minutes, until buttercream is set.
Meanwhile, divide remaining buttercream in 2 large bowls. Add a couple of drops of orange food coloring to each bowl, adjusting shade as desired, to create an ombre effect. Stir to combine, adjusting shade as desired. Transfer each shade of orange, and remaining white buttercream to a piping bag fitted with a coupler attachment.
Pipe darkest-colored buttercream over the bottom half of the side of the 10-inch cake, followed by the light-colored buttercream over the remaining half of the 10-inch cake. Spin the cake turntable, while running the icing smoother over the entire cake, to get a smooth, blended frosting color.
Pipe light-colored buttercream over the bottom half of the side of the 8-inch cake, followed by the light-colored buttercream over the remaining half of the 8-inch cake. Spin the cake turntable, while running the icing smoother over the entire cake, to get a smooth, blended frosting color.
Finally, pipe the white buttercream over the 6-inch cake. Spin the cake turntable, while running the icing smoother over the entire cake, to get a smooth, blended frosting color.
Place the 10-inch cake back on the turntable. Insert 3 cake dowels into the center of the cake. Cut the dowels so they are flush with the surface of the cake. Place 8-inch cake on top of 10-inch cake and repeat with cake dowels. Top 8-inch cake with remaining 6-inch cake.
Transfer remaining shades of buttercream to 3 piping bags fitted with couplers. Using tip K11 pipe a small beaded border, using the white buttercream around the 10-inch cake, 8-inch cake and 6-inch cake base to cover the cardboard cake rounds.
Attach tip K29 on dark-colored buttercream for hydrangea, T02 on medium-colored buttercream for rose, and T02 on white buttercream for apple blossoms. Using tip K01, pipe small decorative dots on and around hydrangea. Pipe apple blossoms and roses onto flower nails, and transfer to cake using a flower lifter. Arrange flowers decoratively down the side of the tiered cake. Pipe hydrangea directly onto the cake.