Watermelon Cake Tutorial

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Well Summer is definitely here where I live in the UK! We are currently enjoying a bit of a heat wave which means it is the perfect weather for a summer party or BBQ. I hope wherever you are reading this the sun is shinning for you too.

So to celebrate the sunshine I thought I would make a cake that would be the perfect summer centerpiece. This watermelon themed cake is really simple to make and is decorated with buttercream and seeds made from black icing. Now it may not look exactly like a round watermelon, but you get the idea! The bit I love most about this cake, is that the sponge cake inside has been coloured to match the coloured buttercream on the outside, so when your guests see you cut into the cake this adds a bit of a surprise!

watermelon cake

For the cake itself I actually used my vanilla sponge cake recipe, which I split into my 6 inch cake tins giving me 4 layers of delicious cake.

Colouring my Sponge Cake

I then coloured a quarter of the mixture with the Sugarflair extra green and the remaining three quarters with the Sugarflair extra red. The great thing about these gel colours is that the paste is highly concentrated, so you only need a small amount to get these vibrant colours which keep their colour when baked. I then coloured my buttercream with the same colours, and  also added in the lighter green shade so that after filling the cake the outside would match perfectly. Oh and I added a lot of chocolate chips to the red layers to look like the watermelon seeds.

watermelon cake


The ingredients you will need to make this 6 inch cake are:
14oz/ 400g – Self Raising Flour
14oz/ 400g – Butter
14oz/ 400g – Caster Sugar
4 eggs
4tbsp – Vanilla Essence / Flavouring
4tbsp – Milk

I love how simple this cake is to make, but how it is so bright and vibrant and really has a summery feel. I really hope you will enjoy the tutorial and find it useful:

If you would like to know how I made the vanilla buttercream in this video then I have another video explaining the ingredients and how I made it (which can be seen here – vanilla Buttercream).

Tools I used

Below is a list of the tools I used to decorate the cake that you might find useful:
Turn Table: http://amzn.to/2CfVJUl
Wilton Icing Smoother: https://amzn.to/2KSRBii
Metal Scrapper Tool: http://amzn.to/2BNjf7v
Piping bags I use: http://amzn.to/2xqeDlM
Sugarflair Extra Green: https://amzn.to/2L5SwuZ
Sugarflair Extra Red: https://amzn.to/2KQQKyo

vanilla sponge cake recipe

Vanilla Sponge Cake Recipe

Author: Cakes by Lynz
This is a perfect all rounder cake! It is light and fluffy and can be used for simple round cakes or 3D carved cakes too.
The cake will be 6 inches x 4.5 inches when decorated.
Prep Time 10 minutes
Cook Time 50 minutes
Decorating Time1 hour 30 minutes
Total Time 2 hours 30 minutes
Servings 6 (6-12 servings)
Recipe Type Cake Recipe
Keyword Sponge Cake, Vanilla


Ingredients the Cake

  • 12 oz Self Raising Flour (340g)
  • 12 oz Room Temperature Butter or Baking Spread (340g)
  • 12 oz Caster Sugar (340g)
  • 4 eggs
  • 2 tbsp Vanilla Essence / Flavouring

For the Buttercream

  • 18 oz Icing Sugar (500g)
  • 9 oz Block of Salted Butter (250g)
  • 1 tbsp Vanilla Essence / Flavouring
  • 2.5 tbsp Milk


For the Cake

  • Place all of the ingredients for your cake together in your mixing bowl.
  • Mix these together until the ingredients are fully combined. This usually takes around 30 seconds.
  • Divide your mixture between 2x 6 inch cake tins. I like to cover the inside of my tins in a thin layer of butter and dust with flour, before adding a circle of parchment to the bottom to stop the mixture from sticking.
  • You then want to bake your cakes for around 45 minutes on the middle shelf at 180 degrees celcius. For my oven I use a normal oven setting. I don’t actually use my fan oven when baking cakes as it tends to bake the cakes quicker on the outside so you get this hard crusty shell and the mixture is not baked all the way through.
  • After 45 minutes you can take a cocktail stick or bamboo skewer and push this into the center of the cake. If it comes out clean you know your cake is baked all the way through. You can then place your tins of a wire rack to let cool for a few minutes before turning them out, and allowing to fully cool.

For the Buttercream

  • Whilst the cake is cooling you will need to sift your icing sugar into your mixing bowl. To this add the butter, flavouring and milk.
  • Then mix your buttercream on a medium speed. After around 5 minutes your buttercream will start to go creamy. You can then add any gel colouring depending on the theme of your cake.

Filling and stacking your cake

  • Once your cake has cooled you can level off the top and divide each layer into 2. Placing your buttercream between your layers, stack your cake.
  • You then want to add a thin crumb coat of buttercream around the edge of your cake to lock in any loose crumbs. Place your cake into the fridge for around 30 minutes to allow the buttercream to firm up.
  • You can then go in with the rest of your buttercream adding a nice finish around the side of your cakes. This is then ready for any final decorations.
    Get all my tips and tricks for covering your cakes in buttercream here!

Also why not save the recipe for later and pin it to Pinterest

Watermelon cake tutorial

Thank you for reading!

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11 Responses

  1. This looks amazing! Can you please tell me what is the black ingredient you use on the finishing touch to make seeds.

    1. Hi Jenny, I am so glad you like the cake. The black seeds were made from black icing / fondant. I hope this helps. Lynz

  2. Hi there – I was wondering if you think this cake would freeze well if it needed to be made a week in advance before icing?

  3. Hi,
    I like your videos, watched a couple. I came to this as I’m looking to colour buttercream red, a nice satin red. I have some questions:
    1) If you make it in advance, does the colour darken? Will Wilton Red work just as well?
    2) Does it leave a bitter or strange aftertaste? I’ve read that some red gel colours make the buttercream taste bad, when added to make a bright red.
    2) Where can you buy it from? (apart from amazon?)
    3) Would this colour affect kids?

    1. Hi, Buttercream will darken the longer you leave it, but for red I usually use the extra red by Sugarflair. It is alot more pigmented so you don’t need as much to get the colour. Also yes some gel colours the more you add it does make the buttercream taste slightly different. It is always hardest to get the really dark colours. In regards to buying the colours if you have a cake decorating shop near you or The Cake Decorating Company is great

  4. I made this for a friend’s 40th last week. We had a socially distanced, outdoor cinema viewing of Dirty Dancing, so the cake fitted perfectly with the theme. It was really yummy and great to try a different recipe as I’ve used the same sponge recipe for years. I will definitely make this again. Thank you.

  5. Hi! I’m planning to make this watermelon cake for my daughter’s TWOtti Frutti themed birthday.
    1) Do you recommend using self-rising vs. cake flour vs. all purpose flour?
    2) Should the butter be salted or unsalted?
    3) Does it make a difference if the eggs are room temperate as well as the butter for this recipe?
    Thank you! Stay safe and well!

    1. Hi Jennifer, I am so glad you like the watermelon cake. To answer your questions, I always use self raising flour. If you use all purpose, plain or cake flour you will need to add a raising agent. Self raising flour already has it added in, but you will need to add baking powder. Add 2 tsp’s of baking powder to each 150g/6oz of plain flour. In regards to the butter I always use salted, but it is entirely down to personal choice. Or you could also use a cake spread like stork for hte cake mixture (always use real butter for buttercream). For the butter you will need this to be room temperature, but for eggs I always use mine from the fridge. I hope that helps x

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Hi, I’m Lynsey and welcome to Cakes by Lynz. I LOVE everything cake! Here you will find all my latest cake decorating video tutorials from my YouTube channel, reviews and general cake ramblings!

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