Rainbow Microwave Mug Cake

Happy Valentine’s Day! On my birthday I shared a Valentine’s Day recipe, so it only seems right that I share a birthday recipe on Valentine’s Day, right? Doesn’t really make much sense to me, either, but that’s what’s we’re rocking with today.

So this, ladies and gentlemen, is my magnificent masterpiece of a microwave mug birthday cake. (Loving the alliteration!) It took me a long time to come up with a birthday cake that seemed fitting for me, being a food blogger and all. After combining my love of single-serving desserts, bright colours, simplicity and quickness, this Rainbow Microwave Mug Cake seemed the only option!

Rainbow Microwave Mug Cake | www.happyhealthymotivated.com

I’m going to jump right in and tell you this rainbow cake doesn’t have a red layer – I know. I did make a red layer, but as soon as I did, I completely changed how I was going to make this cake and that made the red layer completely useless. And I certainly wasn’t going to make the whole thing again! Red is totally overrated, anyway.

On the plus side, this recipe does include enough batter for you to make a red layer and now I’ve sussed the correct technique out for you, you won’t have to skip the red layer in the name of vanity and perfection. I can’t really call it perfection can I? A rainbow without a red section surely isn’t perfection. I think I’m going into this a bit too much.

Rainbow Microwave Mug Cake | www.happyhealthymotivated.com

There’s one key piece of equipment you’ll need to make this Rainbow Microwave Mug Cake – a straight mug. As in a mug that has completely straight up and down sides – no curves. This Hello Kitty mug set is the exact two mugs I used but I didn’t get it from the US Amazon (have you seen that shipping price?!) I got my Hello Kitty mugs from Amazon.co.uk.

Each coloured layer is steamed separately in the microwave and in order for you to be able to stack them on top of each other, they need to be straight and not curved. It’s also handy if you have more than one mug of that exact shape and size so you can prep one layer whilst the other is steaming.

Rainbow Microwave Mug Cake | www.happyhealthymotivated.com

Speed is key to making a success of this Rainbow Microwave Mug Cake. The batter is a basic cake batter which really shouldn’t be left sat in numerous bowls for long periods of time. The longer the batter isn’t cooking, the longer the rising ingredients are left to deteriorate, so the faster you work the better.

Apart from that, this cake is really simple to make! Whip up your batter, separate it into seven different bowls, colour each of them and steam each individually in the microwave. Leave the cakes to cool before slicing, stacking and icing. I swear, it’s easier than it sounds!

Rainbow Microwave Mug Cake Recipe - the easy way to make a beautiful rainbow layered cake is to make it in the microwave! Perfect for St Patrick's Day | www.happyhealthymotivated.com

Rainbow Microwave Mug Cake

5 from 1 vote
Servings 4 tall cakes - about 12 servings


  • 1 cup white sugar 200g
  • 1 3/4 sticks butter softened at room temperature, 200g
  • 4 eggs at room temperature lightly beaten
  • 2 teaspoons vanilla extract
  • 2 cups white flour 200g
  • 1 teaspoon baking powder
  • 1/2 teaspoon baking soda
  • pinch salt
  • red orange, yellow, green, blue, purple and pink food colouring
  • whipped cream
  • oil or butter for greasing


  • Cream the sugar and butter together in a large bowl until light in colour and fluffy in texture - about 3 minutes on medium speed.
  • Crack in the four eggs and pour in the vanilla extract. Beat for another minute on medium until well combined.
  • Sieve in the flour, baking powder, baking soda and salt. Beat on a low speed for about one minute until just combined - don't over-mix!
  • Divide the mixture as evenly as you can between seven bowls.
  • Add a couple of drops of food colouring to each bowl and mix very gently until the colour has been evenly distributed - again, do not over-mix!
  • Use a bit of oil or butter to grease your mug and scoop all the batter of one colour into it, smoothing down the top with the back of a spoon. I steamed each layer in the microwave on full power for 1 minute and 40 seconds. Test your cake after 1 minute 20 seconds by sticking a toothpick in the centre - if it comes out clean of crumbs or batter then it's ready. Keep cooking the batter for an extra 5 seconds at a time until you're happy it's done. When cooked, tip your coloured cake out onto a wire wrack and leave until completely cool.
  • After you've found out how long you need to cook each layer for, continue steaming each layer in the same mug until you've gone through all the colours - don't forget you need to grease the mug each time! Leave them all to cool together on a wire wrack.
  • When cooled, slice each coloured mug cake into four even slices.
  • Stack each cake up in the following coloured combination: red, orange, yellow, green, blue, purple and pink, sandwiching each layer with whipped cream. Serve asap - these cakes fall over!

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About Nicola

I’m Nicola, the face behind Happy Healthy Motivated – your go-to guide to becoming your best you!
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  1. Corinne says

    This is a masterpiece! I wonder if I could do this using my ramekin set since I don’t have a set of mugs that are all straight. My kids would get a big kick out of this!

  2. Julie says

    This is pretty awesome (and I don’t say awesome very often!) Red is my favourite colour but I totally forgive you for the lack of red cake under the circumstances, the overall look is pretty impressive. Also impressive is how you took your photos before the whole thing fell over. I don;t know if I will ever attempt such magnificence but I am certainly pinning just in case!

  3. Nadia says

    TQ soooo much for this recipe!!!! I have to bake a birthday cake for my father in law and I used ur recipe and it turn out to be amazing cake!!! And it only took me 10 minutes to bake it!!! Tq so muchhhh for the recipe!!

  4. Miz Helen says

    Your stack of Mug Cakes looks so pretty, awesome idea! Hope you are having a fantastic week and thanks so much for sharing with Full Plate Thursday.
    Come Back Soon!
    Miz Helen

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