Round to Square Fruit Cake

Our answer

Nigella's classic fruit cake recipes in both Feast and Christmas have tables for 3 different sizes of cake, but to start you need to work out the round tin equivalent for your square tin as most cake recipes give tin sizes for round tins. As a rule of thumb, you take the square tin measurement and add 2.5cm/1 inch to this to get the round tin equivalent.

So in the case of a 25cm/10-inch a square tin you will need a recipe that fits a 28cm/11-inch round tin. If you can't find the appropriate recipe for a 28cm/11-inch tin then we would suggest using 1 1/4 x a 25cm/10-inch round cake recipe - however we would like to point out that we have not tested this, it is our best guess at the likely quantities.

We would follow the baking instructions for the 10-inch round tin, starting the oven at 150c/300F for 1 hour then reducing it to 140c/275F for the remaining time and allowing betwen 20 minutes and 1 hour extra baking time. When the cake is done it will be firm on top and a cake tester will come out clean.

As the sharper edges of a square cake tin can also burn more easily, we would suggest giving the tin a quarter turn in the oven every 30 minutes. Do this carefully, using oven gloves.