Tell me how to make Gluten-Free Ombré Cake.
Here's a recipe for Gluten-Free Ombré Cake:

Ingredients:

Cake

• nonstick cooking spray, for greasing
• 2 lb beet
• 2 cups frozen raspberry
• 2 cups milk
• 3 cups gluten-free flour blend
• 2 cups sugar
• 1 tablespoon baking powder
• 1 teaspoon kosher salt
• 1 cup unsalted butter, softened
• 6 large egg whites
• 1 teaspoon vanilla extract

Frosting

• 1/4 cup gluten-free flour blend
• 2 cups unsalted butter, softened
• 1 teaspoon vanilla extract
• 1/4 teaspoon kosher salt
• 3 1/2 cups powdered sugar

Assembly And Garnish

• 1/2 cup raspberry jam, divided
• 6 oz raspberry

Special Equipment

• cake turntable
• cardboard cake round, 9 in (22 cm)
• offset spatula
• bench scraper

Instructions:

1. Make the cakes: Preheat the oven to 350°F (180°C). Grease 3 8-inch (20 cm) round cake pans with nonstick spray and line with parchment paper.
2. Add the beets, raspberries, and milk to a blender. Blend until mostly smooth. Strain the mixture through a fine-mesh sieve into a medium bowl, pressing the solids with a spatula to extract as much liquid as possible. You should have about 2 cups (480 ml) total. Discard the solids. Reserve 1/2 cup (120 ml) of beet-milk mixture for the frosting. Set the remaining beet-milk mixture aside.
3. Add the flour, baking powder, salt, sugar, and butter to a large bowl. Mix on medium speed with an electric hand mixer for 2–3 minutes, until the mixture is sandy in texture.
4. Add the egg whites and vanilla and mix on medium speed until combined, scraping down the sides of the bowl as needed.
5. Add 2/3 cup (160 ml) of the beet-milk mixture to the batter and beat to combine. Measure 2 cups (230 G) of batter and transfer to one of the prepared pans. Spread in an even layer.
6. Add 1/3 cup (70 ml) more of the beet-milk mixture to the remaining batter and beat to combine. Measure 2 cups of batter and transfer to another prepared pan. Spread in an even layer.
7. Add 1/2 cup (120 ml) more of the beet-milk mixture to remaining batter and beat to combine, then transfer to the remaining prepared pan and spread in an even layer.
8. Bake the cakes for 30–35 minutes, until a toothpick inserted in the center comes out clean and the cake pulls away from the sides of the pan. Transfer the cakes to a wire rack to cool for 5–10 minutes, until safe to handle. Turn the cakes out of the pans and let cool completely on the wire rack. Note: The darkest cake may need to bake for up to 5 minutes longer than the other cakes, as it contains the most liquid.
9. While the cakes cool, make the frosting: In a small saucepan, whisk together the reserved 1/2 cup (120 ml) beet-milk mixture and the flour. Cook over medium-low heat for 2–3 minutes, whisking continuously, until the mixture thickens. Remove from the heat and transfer to a small bowl. Cover tightly with plastic wrap, pressing it directly against the surface so a skin doesn’t form, then transfer to the refrigerator and let cool completely.
10. In a large bowl, use an electric hand mixer to cream together the butter, vanilla, and salt on high speed until smooth. Sift in the powdered sugar and beat on low speed until incorporated and the frosting is smooth.
11. Add 2 tablespoons the beet-flour mixture and beat to combine. Transfer 1/2 cup (55 G) of frosting to each of 2 small bowls.
12. Add 2 tablespoons of the beet-flour mixture to one of the small bowls of frosting and mix to combine.
13. Add 1/4 cup (55 G) of the beet-flour mixture to the other small bowl of frosting and mix to combine.
14. Transfer the two darker frostings to piping bags fitted with 1/2-inch (1 1/4 cm) round tips.
15. Assemble the cake: Place the cardboard round on the cake turntable.
16. Trim off the domed tops of the cakes.
17. Spread a dab of frosting in the center of the cardboard round. Center the darkest cake on the cardboard round. Using an offset spatula, spread about 1/2 cup (55 G) of the lightest frosting over the top of the cake in an even layer about 1/2 inch (1 1/4 cm) thick. Spread 1/4 cup  (80 G) raspberry jam over the frosting. Place the next lightest cake layer on top and repeat frosting and filling with another 1/2 cup (55 G) of the same frosting and the remaining 1/4 cup (80 G) jam. Top with the lightest cake layer.
18. Dollop 1 cup (115 G) of the lightest frosting on top of the cake. Using the offset spatula, spread the frosting in an even layer across the top, starting from the center and working toward the outer edge. Cover the sides of the cake with frosting, working from top to bottom down the sides. Remove and reserve any excess frosting. Holding a bench scraper against the side of the cake, slowly spin the turntable to help spread the frosting into a thin “naked” layer. Remove excess frosting from the bench scraper as necessary. Refrigerate the cake for 20 minutes, until the frosting is set.
19. To create the ombre effect, heap the remaining light frosting on top of the cake. Smooth over the top and push just over the sides, about 1 inch (2 1/2 cm) down. Pipe the medium frosting along the middle 2 inches (5 cm) of the cake. Pipe the darkest frosting along the bottom 2 inches (5 cm) of the cake.  Holding a bench scraper against the side of the cake, slowly spin the turntable to help smooth the frosting, wiping away the excess. Smooth the top and sides.
20. Heap the raspberries on top of the cake.
21. Slice and serve.

Enjoy your Gluten-Free Ombré Cake!