• Rainbow cake (Chris Middleton)Source: Chris Middleton

This spectacular cake is coloured with homemade natural food colouring. Its innocent exterior belies the excitement when it is cut open!






Skill level

Average: 4.3 (146 votes)


  • 675 g (1½ lb/4½ cups) plain flour
  • 2 tbsp baking powder
  • ½ tsp bicarbonate of soda (baking soda)
  • 180 ml (6 fl oz/¾ cup) full cream (whole) milk
  • 2 tbsp natural vanilla extract
  • 1 tsp liquid stevia
  • 375 g (13 oz) butter, softened
  • 170 g (6 oz/½ cup) rice malt syrup
  • 225 g (8 oz/¾ cup) Apple purée (see note)
  • 6 eggs
  • 60 g (2 oz) shredded coconut


Swiss meringue buttercream

  • 150 g (10½ oz) egg white (from about 4-5 eggs) 
  • 260 g (1 lb 2 oz/3¼ cups) dextrose
  • 350 g (1 lb 9 oz) butter, cut into cubes and slightly softened (it should be 
soft enough to leave a dent from your finger when lightly pressed)


Natural food colours

  • 80 g (2¾ oz/2 cups) baby spinach
  • 1 beetroot (beet) (about 175 g/6 oz), peeled and roughly chopped
  • 75 g (2¾ oz/½ cup) frozen blackberries, thawed
  • 1 carrot (about 120 g/4½ oz), peeled and chopped

Cook's notes

Oven temperatures are for conventional; if using fan-forced (convection), reduce the temperature by 20˚C. | We use Australian tablespoons and cups: 1 teaspoon equals 5 ml; 1 tablespoon equals 20 ml; 1 cup equals 250 ml. | All herbs are fresh (unless specified) and cups are lightly packed. | All vegetables are medium size and peeled, unless specified. | All eggs are 55-60 g, unless specified.


Cooling time: 30 minutes

For the food colours, blend (I use a hand-held blender) the vegetables and fruit individually until puréed. Strain through a piece of muslin (cheesecloth), squeezing out as much juice as possible. You will need about 1 tbsp spinach juice, 2 tbsp beetroot juice for two pink cakes (one darker than the other), 5 tsp blackberry juice and 2½ tbsp carrot juice, plus about 1 tsp of each juice per 2 tbsp shredded coconut.

Preheat the oven to 160°C/320°F (fan-forced). Grease five 4 cm (1½ in) deep, 20 cm (8 in) round cake tins and line the bases with non-stick baking paper. If you don’t have five tins, you can cook the cakes in batches. 

Sift the flour, baking powder and bicarbonate of soda into a large bowl and combine. Combine the milk, vanilla extract and stevia in a jug. Beat the butter and rice malt syrup with an electric mixer until light and fluffy. Gradually add the egg, beating well between each addition. Add a spoonful or two of the flour mixture, if it seems like it is splitting. Beat in the apple purée. Fold in the remaining dry ingredients alternately with the milk mixture. 

Divide the cake batter evenly between five separate bowls (I weigh it – about 400 g/14 oz per cake). Stir a different colouring into each bowl, adding a little more colouring if you would like a darker shade. Spoon into the prepared tins, smooth the surface with a spatula and bake for 15–18 minutes, or until a skewer inserted into the centre comes out clean. Remove from the oven and leave to cool for 5 minutes before turning out onto wire racks to cool. 

Turn the oven down to 50°C/120°F (fan-forced). Divide 2 tbsp of coconut between five small bowls and stir about 2 tsp of colouring into each. Keeping the colours separate, spread the coconut on baking trays lined with baking paper and bake for 20–30 minutes, stirring often until completely dry. Set aside to cool.

For the Swiss meringue buttercream, put the egg white and dextrose in a large heatproof bowl. Place the bowl over a saucepan of simmering water (the bowl shouldn’t touch the water) and whisk until the dextrose dissolves and the egg whites are quite warm. Test this by rubbing a little of the mixture between your thumb and forefinger – the mixture should be smooth, not grainy.

Beat the egg white mixture with an electric mixer on medium-high speed until you have a meringue that is thick and glossy, and the side of the bowl is at room temperature when you touch it. This will take about 10 minutes, depending on your mixer. 

With the mixer on medium speed, add the cubes of butter gradually, beating well between each addition, until the meringue is silky smooth. You may find that the mixture will separate and curdle at some point in the mixing process – do not panic, if you keep beating it should come back together. If the room temperature is too warm (around 18°C/64°F is ideal) and the mixture seems quite soft, pop the bowl in the refrigerator for 10–15 minutes to cool it down.

If the cakes are slightly domed, trim the tops off to level them with a knife. 

Put a little dollop of buttercream in the centre of a serving plate and place four strips of baking paper around
the edge. This will help to keep the plate clean of any icing. Place one layer of cake on the prepared plate. Spread about 120 g (4½ oz/¾ cup) of the buttercream over the top, taking it just over the edge. Repeat with the remaining layers, placing the top layer bottom-side up (to achieve a sharp edge). Spread more buttercream thinly over the top and side of the cake. Scrape off any excess buttercream and discard it. This is called the ‘crumb coat’ and will help to keep you final layer of icing crumb-free. Put the cake in the refrigerator for the icing to firm up, about 30 minutes. 

For the final layer of icing, spread the top and side of the cake generously with the remaining buttercream. Sprinkle with the coloured shredded coconut to decorate. The cake can be stored in the refrigerator for several hours before serving, but it is best served at room temperature; otherwise the buttercream icing will be very firm.



• Apple purée helps to add bulk to recipes that have had the cane sugar removed, as well as providing natural sweetness and fibre. Peel, core and roughly chop 4 large apples (about 800 g/1 lb 12 oz). Put the apples and a splash of water in a medium saucepan over medium-low heat. Cover and cook, stirring occasionally, for 8–10 minutes or until tender. Stir and mash the apples, still over the heat, until broken down – they should be mushy and quite thick. Remove from the heat and set aside to cool. It is fine to have a little bit of texture, but if you prefer a smooth sauce, whiz in a food processor or use a hand-held blender and purée until smooth. The purée will keep for 3–4 days in an airtight container in the refrigerator. It also freezes well for a couple of months – portion the purée into small containers or spoon into ice-cube trays, freeze and seal in an airtight container. Makes 600 g (1 lb 5 oz/2 cups).


This recipe is from Incredible Bakes (Smith Street Books). Photography by Chris Middleton.