Step 1
Heat oven to 180C/160C fan/gas 4. Grease a 900g/2lb loaf tin with Trex and line the base and ends with a long strip of greaseproof paper. Put the Trex, golden caster sugar, xanthan gum and gluten-free flour into a large bowl. Then slowly add the eggs, lime juice and vanilla extract. Beat with whisk until it is pale and creamy – the mixture will be very very thick.

Step 2
Spread half of the cake mix into the tin, then scatter over 75g of the fruit. Carefully dot the rest of the cake mix over and gently spread with the back of a spoon. Bake for 50 mins, until an inserted skewer comes out clean.

Step 3
Poke the cake all over with a skewer. Put remaining 75g fruit into a bowl with the granulated sugar. Stir in the citrus juice, first with a fork, mashing a little of the fruit as you go. If it’s a bit dry, add a splash more juice and spoon over the cake. Leave in the tin until the cake is cool and the topping is set and crisp.