Preheat the oven to 180'C / Fan 160'C / Gas Mark 4. Line a 2lb loaf tin with baking paper and set to one side.

Add the caster sugar, butter, eggs, flour and xanthan gum to a large mixing bowl and beat with an electric mixer until it forms a thick batter with no lumps.

Pour half the batter into a second bowl, so you have two bowls with an even amount of batter in each. In one bowl, add the zest of two oranges and mix together well.

Blend the strawberries (or mash with a fork) and add to the second bowl along with a couple of drops of pink food colouring (if using). Mix well until fully combined.

Take spoonfuls of each batter and randomly place them into the lined loaf tin - there doesn't have to be a specific patter, just dollop them in at random! Once all the batter is in the tin, use a knife to gently swirl the mixture. Don't over-mix as you'll blend the two colours together.

Smooth out the top of the cake and bang on the worktop firmly once to ensure there are no air bubbles. Place in the oven and bake for 50-55 minutes, until the cake is golden on top and well risen, and a skewer inserted in the middle comes out clean.

While the cake is cooking, make the syrup. Pour the orange juice and caster sugar into a saucepan and place on a low heat. Bring to the boil and simmer for 1-2 minutes, then remove from the heat.

When the cake is done, remove from the oven and place on a cooling rack. While the cake is still hot, prick all over with a skewer and then spoon over the syrup to ensure it's all covered. Leave to cool completely.

Once the cake is cool, make icing by mixing the icing sugar and orange juice until it forms a thick paste. Pour over the cake, smoothing out to cover. Decorate with fresh strawberries and extra orange zest before slicing and serving.