Step 1

Position a rack in the center of the oven and preheat to 350ºF. Grease a 6-inch round cake pan with softened butter and line the bottom with a round of parchment paper cut to fit.

Step 2

In a large bowl, whisk together the sugar, oil, egg, beet puree, buttermilk, lemon juice, vinegar, and vanilla.

Step 3

Place a strainer over the bowl and add the teff, sweet rice, and oat flours with the cocoa powder, baking powder, baking soda, and salt. Sift the flours into the beet mixture and whisk or stir to combine.

Step 4

Scrape the batter into the prepared pan and bake until the cake springs back to the touch and a toothpick inserted near the center comes out with moist crumbs, 35-45 minutes. Remove from the oven and let cool slightly, then invert onto a wire rack, peel away the parchment, and let cool completely. The cake can be stored covered at room temperature for 1 or 2 days.

Step 5

Make the cream cheese frosting as directed. Divide into 4 bowls. Leave one bowl white. To the second bowl, add a big pinch of beet powder. To the third bowl add ¼ teaspoon beet powder. And to the fourth bowl add 1 teaspoon beet powder. Stir each bowl well, adding more color if you like (the color continues to intensify as the frosting sits).

Step 6

Cut the cake into two even layers using a serrated knife. Place the bottom half on a serving plate, cut-side up. Place the top half on a rimless plate or cutting board cut-side down. Layer the frosting into a large piping bag fitted with a large star tip, starting with the white frosting and ending with the most vibrant frosting. Pipe a line of frosting on the bottom cake layer, following the curve of the cake. Repeat with the top cake layer. Return to the bottom cake, and pipe another row of frosting next to the first. Repeat with the upper layer. Continue until both layers are covered in frosting; you should have just enough frosting to cover both layers, though if your frosting is extra fluffy, you’ll have a bit left over.

Step 7

Carefully place the top cake layer over the bottom cake layer. The cake is best served at room temperature, though it’s easier to cut when cold. Optionally chill the cake until firm, then cut it into wedges using a large chef’s knife dipped in hot water and wiped clean between cuts, then let the slices come to room temperature before serving. Store leftover cake refrigerated airtight for up to 3 days; serve at room temperature.