Caster Sugar Substitute

Our answer

Caster sugar/castor sugar/superfine sugar is a fine form of granulated sugar. It is used in baking as it dissolves more quickly than granulated sugar. In the UK granulated sugar tends to have quite large granules so is not suitable for baking. However in the US granulated sugar tends to be finer and can be used for baking in some recipes, particularly if the butter and sugar are creamed together for a while at the beginning of the recipe. For meringues we would always recommend using caster or superfine sugar.

You can make your own caster sugar by grinding granulated sugar slightly in a food processor or blender (or a very clean coffee grinder). However you do need to be careful when doing this as it can be easy to end up with a sugar powder instead of finer granules.

We assume you are referring to Nigella's Damp Apple and Almond Cake from Feast (and see link below). For this particular cake the sugar is processed with the apple puree and other cake ingredients and if you can only get granualted sugar then you could whiz the apple puree and sugar together briefly, until it no longer looks like the sugar is in large grains, before adding the other cake ingredients.

http://www.nigella.com/recipes/view/apple-and-almond-cake-for-passover-and-any-other-time-3204