Pink Grapefruit ‘Spare’ Cake

I love grapefruit. Especially pink grapefruit. No added sugar, freshly peeled, first thing in the morning or as a pick-me-up afternoon snack. I love the tangy sharpness with a hint of sweetness and they smell divine.

I’ve wanted to bake a grapefruit cake for ages, but kept forgetting that I wanted to. This may or may not have had something to do with my caramel obsession, bundt obsession, passion fruit obsession and blood orange obsession. Then, when Beca baked her grapefruit sponge on the Great British Bake off it reminded me how much I wanted to use grapefruit in a cake.

This week, we had an unusual cake club event – I won 50kg of ready-to-roll icing from Renshaw in a competition on the Clandestine Cake Club website. As the kind-hearted group organiser I am, I wanted to share this with everyone in the club, so I organised an event for everyone to get together and play with the icing. Themed ‘Naked Cakes’, 15 bakers got together with their plain sponges and Renshaw professional cake decorators came along to show us some sugar craft techniques.

So, here’s a confession *whispers* I don’t really like icing. It’s too sweet, I don’t like the smooth but gummy texture and the way it disguises the lovely cake underneath it. Yes it makes cakes look pretty but it doesn’t add anything to the flavour. It’s so disappointing to cut into a beautifully iced cake to find a plain sponge without any interesting flavour. It’s the reason I didn’t even really like cake until I discovered there was more to cake than victoria sponge! For me, the joy of cake is in the flavours. Anyway, getting back to the cake….

I thought I should bake a sponge for the decorating event that had a punchy flavour, which would hopefully balance out the sweetness of the icing. Not orange again (bit of an orange overdose lately) or lemon (done lemon loads). Grapefruit was the answer. Off I toddled to Pinterest for some inspiration.

There were a few different recipes but I needed to work with what I had, and something that would stand up to the weight of the icing. Also I’d planned to bake a spare cake for the event, so that people could take their decorated sponges home but still have cake to eat on the night! So this is what I did.

I based my sponge on this recipe from Suzonne Stirling’s Urban Comfort blog, which was a lovely big but sturdy cake mix (5 eggs!) and used it for my 6″ decorating cake and the spare cake.

This is the 6″ cake baked for decorating.

Here’s the recipe. Please note this made TWO cakes – one very deep 6″ sandwich cake and one 8″ normal-size sandwich cake. You can use whatever tins you prefer – make two cakes, or one big one. Either adjust the recipe quantities or the baking time.


  • 400g plain flour
  • 300g unsalted butter
  • 540g caster sugar
  • 1tbsp baking powder
  • ¾ teaspoon salt
  • 300mls whole milk
  • 2 tsp vanilla extract
  • 5 eggs (I used large)
  • zest of 1 ½ pink grapefruits (finely grated)

For the filling

  • 100g unsalted butter at room temperature
  • 200g icing sugar
  • pink grapefruit juice and zest

For the topping

  • icing sugar
  • pink grapefruit juice
  • zest strips to decorate


  • Preheat the oven to 180 degrees and prepare your chosen tin.
  • cream together the butter and sugar until pale and fluffy, scraping down the sides and bottom of the bowl as necessary.
  • in a separate bowl, sieve the flour, baking powder and salt together.
  • add the eggs to the butter and sugar mix one at a time, slowly, making sure they’re fully incorporated.
  • add the vanilla
  • mix in the flour, alternating with the milk and mixing slowly.
  • add the zest and mix on a low speed until the batter is smooth, thick and fluffy. If it looks a bit curdled keep mixing for another minute or so until it comes together.
  • pop equal amounts of batter into your chosen, prepared tins. Cooking time will vary depending on what size you’ve chosen. My 8″ sandwich tins took approximately 25 minutes but keep an eye on them and take them out when browned all over, and when the sponge springs back when touched, or a skewer comes out clean. Allow to cool in the tins for 5 minutes and then turn out onto a wire rack to cool fully.
  • For the buttercream, reduce the juice of one grapefruit in a saucepan until it’s thick and syrupy (no sugar needed) and allow to cool. Beat together the butter and icing sugar until light and fluffy, adding the thick juice and a sprinkling of finely grated zest. If you wish to make more, to fill and top your cake(s) with buttercream adjust the quantities as required simply keeping the ratio 2:1 icing sugar:butter.
  • Once cooled, fill your sponges, spreading your buttercream with a pallet knife. I don’t like too much filling – about 1cm thickness does the trick for me.
  • To top with glacé icing, simply add small amounts of pink grapefruit juice to icing sugar and stir until it makes a very thick paste. I found it turned a really pretty pale pink colour. Spread this over the top of your cake, using a few small strips of zest to decorate. Don’t worry if you make it a bit too runny and it drips over the sides – it looks pretty!

And TA-DA! Your pink grapefruit spare cake is done.

Pink Grapefruit Spare Cake

For anyone interested in how the cake decorating turned out, I was pretty pleased with my efforts and definitely learned a lot about the basics of cake covering. Also, I like doing icing roses!