Rainbow Cake

By efriend

Ingredients

• Ingredients:
• 1 1/2 sticks unsalted butter, room temperature
• 2 cups granulated sugar
• 5 large egg whites, room temperature and lightly whisked
• 1 1/2 tsp vanilla paste
• 1/2 cup sour cream, room temperature
• 3 cups all-purpose flour
• 1 Tbsp baking powder
• 1 tsp baking soda
• 1/2 tsp salt
• 1 cup whole milk
• Soft Gel Paste***( Super Red, Lemon Yellow, Electric Orange, Electric Green, Electric Blue and Royal Purple)
• talian Meringue Buttercream
• 12 oz granulated sugar
• 3 oz water
• 3/4 cup egg whites
• 18 oz unsalted butter, cut into 1-inch cubes, room temperature

Details

Adapted from thelittleepicurean.com

Preparation

Step 1

Directions:
Preheat oven to 350 degrees F.  Gather as many 9” round cake pans as you can find.  I only had two, so I had to clean the pans between baking.  Butter and line the cake rounds with parchment paper rounds.  Set aside.
In a bowl of a stand mixer with the paddle attachment, cream butter.  Add sugar and continue to cream until lighter in color.  Slowly add egg whites to the butter on low-medium speed.  Add vanilla paste and sour cream.  Mix until thoroughly combined.
In a medium bowl, whisk together flour, baking powder, baking soda and salt.
Alternate adding flour mixture and milk to the creamed mixture.  Add the flour in three additions, beginning and ending with the flour.
If you have a kitchen scale, transfer the batter to another bowl and weight it out.  Take the weight and divide it by 6.  My total weight was 1530 grams.  Divide by 6, it was 255 grams.  Measure of 255 grams of batter into 6 small bowls.  If you don’t have a scale, it was roughly 3/4 cup of batter into 6 bowls.
Add food coloring to individual bowls.  I used about 4-8 drops of coloring for each.  Some colors required more gel than others to get the vibrant hues I wanted.  Be sure to use food gels.  Adding liquid food coloring will make your batter too runny and thin.
Transfer colored batter to prepared cake pan. Bake for 13-15 minutes until cake is set.  Let cool in pan for 3 minutes before unmolding and allowing to cool completely on the racks.  Continue to bake off cakes until you have completed all six colors.

Directions:
1. In a saucepan, combine sugar and water. Stir until it resembles wet sand. Set to high heat and cook and cook until candy thermometer reads 245 degrees F. While the heat is on, DO NOT stir or disturb the sugar solution. Agitation will cause unwanted cystallization. If any sugar splashes onto the sides of the saucepan, use a clean pastry brush soaked in water to dilute any crystal formation.

2. While the sugar is cooking, whip the egg whites in the bowl of a stand mixer with a whisk attachment. Keep it at low speed until whites are foamy (it should look like the foam on top of beer). Once foamy, begin whipping at medium speed. Before you add the sugar, lower the speed slightly.

3. Once sugar reaches 245 degrees F, pour it into the whipping egg whites in a slow and steady stream. After all the sugar has been added, increased the speed to high. Continue to whip until the mixing bowl is slightly warm than room temperature to the touch.

4. Turn down the mixer to medium speed and slowly add the butter, a couple cubes at a time. Continue to whip at medium speed until all the butter has been added. Whip until buttercream is smooth and creamy.

Notes: If you add the butter when the meringue is too hot, it may melt and the buttercream may not emulsify. If this happens, place the mixing bowl in the freezer for a couple minutes to cool down the mixture. Once cooled, started whipping again.

If the butter is too cold when added to the meringue, the buttercream may end up chunky. Use a torch to warm the bowl or place over a bain-maire to soften the butter.

Cake Assembly

1. Place the purple layer of cake on a cake board. Spread a rounded 1/4 cup of buttercream on top. Repeat with blue, green, yellow, orange and red.

2. Use 1/2 a cup of buttercream for the crumb coat of the cake. Let chill in the refrigerator for 15 minutes. Once chilled, coat the cake with another layer of buttercream.