Preparation

Preheat the oven to 350°F (175°C). Grease the cake pans with butter or line the pans with parchment paper to make the cake easier to release after baking.

Step 1: Make the Sweet Potato Puree

Peel and chop 2 medium purple sweet potatoes. Boil them in water for 15–20 minutes and drain the water. Then, mash the sweet potatoes until smooth and let it cool a bit.

You need to reserve some sweet potato puree for the frosting. You will need 1/2 cup of puree for the batter and 1/4 cup of puree for the frosting. This recipe uses approximately 3/4 cup of potato puree.

Step 2: Prepare the Batter

In a mixing bowl, combine the softened butter and sugar. Using an electric mixer, beat the mixture on medium speed until it is light and fluffy. This should take about 3 to 5 minutes.

Beat an egg into the mixture; then add the next egg and beat until it is mixed in. Do this with each egg and then mix in the vanilla and the salt.

In another bowl, combine the baking powder and the flour.

Add the flour mixture and the milk to the butter mixture, with the flour coming in first and last. Keep the mixer on low speed until the mixture is combined. Be sure not to over mix.

Fold in the 1/2 cup of sweet potato puree. The batter should turn a light shade of purple.

Divide the batter into the two prepared pans.

Step 3: Bake

Bake for 25–30 minutes. To check for readiness, insert a toothpick into the center of the cake. If the toothpick is clean, it is ready.

Rotate the pans halfway through baking to ensure even baking.

Remove from the oven and leave in the pans for 10 minutes. Then transfer to a cooling rack to cool completely.

Step 4: Prepare the Frosting

Beat softened butter until creamy.

Add powdered sugar gradually while mixing on low speed.

Add the 1/4 cup of the purple puree, vanilla, salt, and milk. Mix until smooth and pipeable.

Assemble the Cake

Put one cake layer on a serving plate. Spread a layer of frosting on top.

Add the second layer and frost the cake all the way around until fully covered in a smooth layer of frosting.