Ruby Grapefruit Sponge Cake

One of the things I love about winter is the abundance of citrus, so when I had a bowl of these ruby red grapefruits sitting around uneaten, I thought, why not make a citrus sponge?! It’s one of those cakes that looks pretty fancy, but isn’t difficult to make at all! The secret is making the sponge light and fluffy, and then anything you pair with it will instantly be elevated.

I love using ruby red grapefruits as they’re sweeter than normal grapefruit but still have some tartness without being too sour. You could, of course, substitute the grapefruit for oranges, lemon, lime, tangelo, cumquat, mandarin, pomelo or yuzu.

I’m going to try a yuzu version next as I’ve never had yuzu and I’m rather fascinated by it!

The sponge part of the recipe is based on the basic sponge cake from and it works really well every time, although, I find with almost every sponge cake I make, I can never seem to get the height I want in order to split it into 2. So, for this recipe, everything has been doubled so you have 2 decent sized sponge bases. If you want to go smaller and simpler, then just halve everything below or use the quantities in the Taste recipe link above.

Cottonwood and Co - Ruby Grapefruit Sponge Cake

Cottonwood and Co - Ruby Grapefruit Sponge Cake

Cottonwood and Co - Ruby Grapefruit Sponge Cake


2/3 cup plain flour

2/3 cup self raising flour

2/3 cup corn flour

1/2 teaspoon salt

8 x eggs (at room temperature)

1 & 1/4 cups of caster sugar

2 x 225g block of cream cheese (for filling)

1/2 cup of icing sugar

3 x large ruby red grapefruits

Pansies or other edible flowers for decoration


If you’re dairy intolerant or don’t like cream cheese then just do a straight forward citrus icing mixture (see below) by mixing 3-4 cups of icing sugar with a couple of tablespoons of the grapefruit juice (enough so it’s spreadable). 



Step 1
Grease 2 x deep, 20-25cm round cake tins and line bases with baking paper. Sift flours and the salt together three times to aerate. Preheat oven to 180C.
Step 2
In a separate bowl, pour in the caster sugar and zest the rind of 1 grapefruit over the sugar. With your hands, massage the grapefruit zest into the sugar. This will release the grapefruit oils into the sugar and give the sponge a very subtle citrus flavour.
Step 3
Using an electric mixer, beat eggs and the citrus infused sugar in a large bowl on medium-high speed for 6-8 minutes, or until mixture is thick, pale and tripled in volume.

Step 4

Gradually sift flour mixture over egg mixture while simultaneously, and gently, folding in with a large metal spoon until just combined. Divide the mixture equally between prepared tins. To level batter, gently spin tins on kitchen counter. Bake for approx 20-25 minutes, or until cakes have shrunk away from the sides slightly and spring back when gently touched.
Step 5
Turn the cakes out on to baking paper-lined wire racks. Carefully peel away baking paper, then leave to cool.
Step 6
While the cakes are cooling, mix the cream cheese (room temperature) in a bowl (with electric mixer or whisk) with 1/4-1/2 cup of icing sugar (or until desired sweetness), a tablespoon of milk (if required) and the zest of the other 1-2 grapefruits – until mixture is smooth and it has a nice sweet tart flavour. Add a little more milk if needed or until the cream cheese mixture is easily spreadable (the consistency of nutella or smooth peanut butter). If it’s too thick it will be hard to spread over the sponge.
Step 7
Once the sponges are cool, spread approx 1/3 of the citrus cream cheese over the base sponge, then place the 2nd sponge on top and cover both sponges with the remaining cream cheese mixture. Decorate the top with grapefruit segments and edible flowers like pansies. Just make sure you remove the membrane and pith of the grapefruit (the white bits) as both are very bitter and also don’t look very pretty. The grapefruits can also be very juicy & wet so if they are just blot with a paper towel to dry or you could always try dehydrated grapefruit on top?
As mentioned above, if you don’t like cream cheese or want something lighter and sweeter, make a plain icing by combining 3-4 cups of icing sugar with approx 1/3 cup to 1/2 cup of grapefruit juice – enough so it’s a spreadable, thick drizzle, but not so thin that it’s totally runny (if it is too runny, add more icing sugar). Spread 1/3 over the base sponge, add the 2nd sponge and drizzle the remaining icing over the top. Decorate as above.
For edible flowers you can’t go past pansies as they are so pretty and come in just about every colour imaginable. Given it’s winter here, I went for the orange and purple one which is perfect for a winter citrus sponge.

Cottonwood and Co - Ruby Grapefruit Sponge Cake

I really love this ruby grapefruit sponge as it’s a little different but also has that lovely, subtle sweet and tangy citrus flavour. It really would work beautifully with any citrus though so give it a try if you have a bowl full of citrus fruits that you don’t know what to do with!

And if you make it, please let me know how it turned out!

N x

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  1. This looks and sounds amazing. I’m going to whip one up sometime soon. My mum was the queen of baking when I was growing up – all on a coal range – I don’t know how she did it with such variable temperatures but she did. Her sponges were legendary and she had a trick that ensured they were super light – it’s not for the faint-hearted! Once the batter is in the pans and before you pop them in the oveN, take a pan, hold it at hip height then let it fall to the ground! Then repeat with the other one. It forces air into the batter. Weird I know – and the potential for disaster is high on the first go or so – but it always worked a treat!

    1. hahaha! Oh Jos I had a giggle reading that tip as I’ve never heard of it and how bizarre it worked?! Wonder if she dropped them one day by accident and found the sponge turned out lighter?!!! haha. I’m so intrigued i’m going to have to try that now – will have to make sure I drop it dead flat as I’d imagine a batter splatter would not be fun to clean up haha. Did it work for you when you did it? I love hearing baking stories from way back. Nicki xo

      1. Jossie Budge says:

        It totally worked Nicki but it takes precision and grit as it is a weird thing to do!!!!. I never thought twice about her little quirk until a friend was over one day and saw her do it thought the entire situation bizarre! Kudos to you on perfecting the sponge – it isn’t easy and pav can be tricky too – it takes time and patience. I’m impressed. (Side note – did you get a copy of the KRB cookbook that came out about four years ago? My son went there and I edited it. Such a beautiful book. Alexx told me you were in Nat’s year).

  2. You really make it seem so easy together with your presentation however I find this topic to be actually one thing that I feel I’d by no means understand. It kind of feels too complicated and very vast for me. I’m taking a look ahead for your next post, I’ll try to get the grasp of it!

    1. Don’t worry, I know what you mean! I was terrible at baking but the more I am practicing, the better, and easier, I am finding it. I’ve got a beautiful pavlova recipe coming up on the website soon and that is about the easiest thing you can ever make, so maybe that might be a good starting point for you? 🙂

  3. Nicki this looks wonderful, the ruby grapefruit sounds just perfect! I’m a fan of winter citrus too, any citrus really 🙂

    1. Thanks Sally! I’m certainly no recipe developer but thought why not try grapefruit instead of your typical orange and lemon. Yuzu is next, of course! x

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