Rainbow Frosted Sheet Cake. Moist yellow cake enrobed in a blanket of rainbow swirled swiss meringue buttercream. A simple delicious cake.
I’m hoping someone out there shares my love for pastel rainbows, swiss meringue buttercream and easy peasy sheet cakes that are just darn good because thats exactly what we have here today, Rainbow Frosted Sheet Cake.
You know what I love about a sheet cake? There’s no intimidation. Seriously, think about it for a minute. Those gorgeous decorated layer cakes (which I’m obsessed with BTW) are intimidating. They are “too beautiful to cut” or “how do you cut this?” or my favorite, “you brought it, can you cut it for everyone?”. I can tell you first hand, I can make a beautiful layered cake but that does not make me good at cutting it, lol.
Enter the Rainbow Frosted Sheet Cake, one layer of golden buttery vanilla cake swirled in smooth colorful swiss meringue butter cream. No special cutting requirements here, no fear of digging that knife right in and staking your claim. No fancy cake server, a plastic knife will do! No balancing acts trying to get your slice to the plate. No sooner is it cut and you’re taking the first bite!!
The Rainbow Frosted Sheet Cake is exactly what you’ve been looking for. Simple, delicious and beautiful!
Here are some of the products I used to make this Rainbow Frosted Sheet Cake:
- Nielsen Massey Vanilla Paste – There’s nothing like it and it breaks my heart when I run out! You use it just like you would extract.
- Wilton Food Colorings – This box includes a variety of colors that I use often.
- King Arthur Unbleached Cake Flour – I use King Arthur products regularly including the is flour
- 9×9 non-stick pan – I use this pan for everything, bar cookies, brownies you name it. Its non-stick to so I can just line it with parchment and go.
Please note some of the links above are affiliate links which means if you purchase from the link I get a small commission. I use these products and stand behind them which is why I chose to tell you about them. Thank you for your support.
FORGOT TO PIN IT? Here you go! Thanks.
- 1½ cups cake flour
- ½ cup milk
- 1 stick butter room temp
- ¾ cups sugar
- ½ Tbsp baking powder
- ¼ tsp salt
- 2 tsp vanilla paste (or extract)
- 2 large eggs room temp
- 3 eggs whites
- ¾ cups sugar
- 2½ sticks butter (or 1¼ cup) room temp, cut into Tbsp size chunks.
- 2 tsp vanilla extract.
- Sugar crystals for decoration (optional)
- Preheat oven to 350 degrees F
- Line 9x9 pan with with parchment so it hangs over the side so you can pull the cake out once cooled.
- Measure out flour, put in small bowl set aside.
- Measure out milk, put in small bowl, set aside.
- In mixing bowl add butter, sugar, baking powder, salt and vanilla.
- Mix on med/high until light and fluffy.
- On medium speed add in one egg at a time, mix until well combined.
- On low speed add the milk and flour, alternating until all add. Increase speed to medium.
- Mix until well combined.
- Pour batter into prepared pan.
- Bake for 30 min or until golden brown and tooth pick inserted comes out clean.
- Cool completely.
- In medium sauce pan add the egg whites and sugar.
- On medium heat you are going to whisk egg mixture until sugar is completely dissolved (you can test it by rubbing a small amount between your fingers to test it, it should be completely smooth).
- Transfer to mixing bowl and with whisk attachment whisk on high until stiff peaks form and mixture is cooled.
- On low speed add the butter one piece at a time. Mix until well combined.
- Switch to paddle attachment, add vanilla, mix until smooth and glossy.
- Divide buttercream into 6 small bowls or cups.
- Color each cup differently, I used pink, orange, yellow, green, blue, purple by Wilton.
- Each cup of buttercream will be divided in half, plop half of each color randomly onto cake. Repeat with the second half of the buttercream.
- Swirl the colors and spread the buttercream with a offset spatula or regular spatula.
- Sprinkle with sugar crystals (optional).
- When ready cut and serve.