A delicious vanilla cake with sprinkles stirred into the batter to make spots of bright color throughout. Perfect for a vegan birthday cake! Deliciously moist and sweet, this rainbow cake is perfect for a birthday party.
Preheat oven to 350F (180C). Lightly grease two 8" baking pans and line the bottoms of the pans with a circle of parchment paper.
In a large bowl, whisk together the all-purpose flour, white sugar, baking powder, and salt. Now add the non-dairy milk, light oil, and vanilla extract and stir to combine. It will make for a very thick batter, almost like cookie dough.
In another large bowl, use a stand mixer or hand beater to combine the aquafaba and cream of tartar until it forms stiff peaks. This will take about 3 to 6 minutes.
Now fold the aquafaba into the batter. The batter is thick and it will take a bit of time to combine the two, so be patient. When the batter is combined you can lastly add the sprinkles. Depending on the kind of sprinkles you have they may bleed, so working quickly, scatter the sprinkles over the surface of the batter and then quickly give it 2 to 4 stirs to combine. It’s ok if the sprinkles aren’t mixed in perfectly, they will do their thing in the oven, it’s more important that they don’t bleed.
Divide the batter evenly among the two pans. Bake for 35 to 42 minutes until a toothpick inserted in the center comes out clean. Let cool completely before frosting.
In a large bowl, use a stand mixer or hand beater to mix together the vegan butter, vegetable shortening, powdered sugar, and vanilla extract until fluffy. Add 1 - 4 tablespoons of non-dairy milk as needed to reach desired frosting consistency.