A blend of gluten-free flours including brown-rice flour, almond flour, and quinoa flour yield delicate results. Buttermilk helps to keep the cake super moist, and plenty of cocoa powder makes it taste rich and decadent.
Make the cake layers: Preheat oven to 350 degrees. Lightly coat two 8-inch cake pans with cooking spray. Line bottoms with parchment; spray parchment.
Whisk together dry ingredients in a large bowl. Add remaining ingredients, and mix until smooth, about 3 minutes. Divide batter between pans.
Bake cakes until they pull away from sides of pans, about 1 hour. Let cool in pans on wire racks. Cakes will keep, covered, for up to 1 day.
Make the frosting: Place sugar, water, corn syrup, and whites in a heatproof mixer bowl over a pot of simmering water. Cook, whisking occasionally, until sugar dissolves and mixture registers 160 degrees on a candy thermometer.
Attach bowl to mixer. Whisk hot sugar mixture on high speed until stiff, glossy peaks form, about 7 minutes. Whisk in vanilla and salt.
Assemble the cake: Place a cake layer on a plate. Spread 2 cups frosting on top. Place remaining cake layer on top of frosting. Frost top and sides with remaining frosting. Cake is best eaten within 1 hour of frosting.
We've tinted the finished frosting pink by adding red gel-paste food coloring drop by drop. Feel free to leave it white, or tint it with any favorite color.