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Watermelon Faultline Cake

Is it a watermelon...No it's a CAKE!

about 16 - 18 slices

Medium 150 Minutes



For the recipe  Watermelon Faultline Cake

For the Cake:

330 g Margarine
330 g Caster Sugar
6 Medium Eggs (beaten)
15 ml Dr. Oetker Madagascan Vanilla Extract (1 tbsp)
12.5 g Dr. Oetker Red Extra Strong Food Colour Gel (2 1/2 tsp)
330 g Self-Raising Flour
150 g Dr. Oetker Dark Chocolate Chips

For the Swiss Meringue Buttercream:

200 g Egg Whites (about 6 medium egg whites)
400 g Caster Sugar
500 g Unsalted butter (room temperature)
15 ml Dr. Oetker Madagascan Vanilla Extract (1 tbsp)
10 ml Dr. Oetker Green Extra Strong Food Colour Gel (2 tsp)
2.5 g Dr. Oetker Red Extra Strong Food Colour Gel (1/2 tsp)

For the Decoration:

50 g Dr. Oetker Dark Chocolate Chips
5 ml Dr. Oetker Green Extra Strong Food Colour Gel (1 tsp)




For the Cake

Preheat the oven to 180°C (160°C Fan/Gas Mark 5), Grease and line 4x6” round cake tins. Place the margarine and sugar into a free standing mixer and beat together until smooth and pale in colour.


Add the eggs and Vanilla Extract and mix until a smooth mixture is formed, scraping down the sides of the bowl as required. If the mixture begins to curdle add a spoonful of flour.


Mix in the Red Colour until the colour is evenly distributed. Sieve in the flour and fold into the mixture until all the flour is combined. Finally pour in the Chocolate Chips and stir through the cake batter.


Divide the mixture evenly between the 4 cake tins and place in the preheated oven. Bake for 30-35 minutes until the cake have risen and a skewer inserted into the centre of the cake comes out clean. Once baked allow to cool in the tins for 15 minutes and then place on a wire rack to cool completely. 


For the Buttercream

Whilst the cakes are cooling, make the buttercream. Make sure your mixer bowl is clean and dry, place your egg whites and caster sugar into your clean mixer bowl and place the bowl over a pan of barely simmering water making sure the water doesn’t touch the bottom of the bowl. With a balloon whisk stir the mixture until the sugar has dissolved – this will take about 5-10 minutes. To check the sugar has dissolved rub some of the mixture between your fingers and it should be smooth, if you can still feel the sugar crystals continue to heat the mixture. 


Once the sugar has dissolved remove the bowl from the heat and place on your freestanding mixer with the whisk attachment. Whisk on a medium to high heat until the bowl is cold to touch and the meringue mixture forms stiff peaks – this should take about 8 - 10 minutes. It is important the mixture is completely cool before moving onto the next step. 


Chop the butter into small cubes, on a medium mix speed add the cubes of butter one at a time into the meringue mixture. Once all the butter has been added turn the mix speed up to high and whisk the buttercream until the have a glossy, smooth buttercream – the buttercream may curdle once all the butter has been added, don’t worry if this happen whilst mixing on a high speed the buttercream will come together. 


Finally add the Vanilla Extract into the buttercream and mix through.


Divide the buttercream into two bowls placing half the buttercream in each bowl.


To Assemble the Cake

Flatten the top of each layer of cake, do this by cutting any domed tops off each cake.


Place a small blob of buttercream onto your cake board or serving plate. Place a cake layer on top. Take one bowl of buttercream, this will be to fill and crumb coat the cake. Place a few spoonful of buttercream onto the cake layer and smooth out using a palette knife, place another cake layer on top and repeat until all your cake layers have been added. Now crumb coat your cake by smoothing buttercream around the edge and on top of the cake. This should only be a thin layer of buttercream so you should be able to see the cake sponge through some areas of the buttercream. To create a smooth finish run a large palette knife dipped in boiling water around the edge and top of the cake. Place the cake in the fridge for 30 minutes to chill and allow the crumb coat to set. 


Whilst the cake is chilling colour the remaining buttercream for the coating.  Take the remaining buttercream, place ¼ of the buttercream into another bowl and add ½ tsp Red Colour Gel and mix through until the colour is evenly distributed through the buttercream.


Add 1-2 tsp of Green Colour Gel to the remaining buttercream and mix until you have a shade of green you are happy with for your watermelon.


Once the cake has chilled remove from the fridge and using your red buttercream smear a ring of red buttercream around the edge of the cake about 6cm high, use a pallet knife to smooth the buttercream. 


Place the green buttercream into a piping bag a cut the end of the piping bag to make about a 1cm hole. Pipe ring of green buttercream around the cake leaving the red buttercream exposed. Use a large pallet knife to smooth the buttercream, this should create the uneven faultline around red buttercream. Finally smooth the top of the cake with green buttercream. 


To Decorate the Cake

Place the remaining Chocolate Chips into the red buttercream to look like seeds. Place a small amount of buttercream into a bowl and using a small paint brush, paint around the edge of the faultline to define the line. 


Paint vertical stripes down the watermelon with the green colour and using the paint brush to smudge the lines and blend into the green buttercream.


Your cake is now ready to serve and surprise your guests! 

To create the domed cake top, replace one of the round cake tins with a domed cake tin or carve the top sponge layer into a dome shape.

Nutritional Information for the recipe Watermelon Faultline Cake

Per Serving Per 100 g / ml
Energy 2864 kJ
684 kcal
1813 kJ
433 kcal
Fat 43.66 g 27.63 g
Carbohydrate 66.57 g 42.13 g
Protein 6.54 g 4.14 g