I have baked the Autumnal Birthday Cake twice. Is the sponge supposed to be dense when cooked?
Nigella's Autumnal Birthday Cake (from HOW TO BE A DOMESTIC GODDESS) is a maple-flavoured cake with a marshmallowy icing. The cake itself uses maple syrup as a sweetener and a flavouring and this means that the cake will not have the same open and spongy texture as a Victoria sponge but will have a slightly closer, moist texture, though it should not be heavy.
The cake should rise well when baked. If it is not rising then check that your self-raising flour is still in date as the raising agents in the flour become less active over time, particularly in humid environments. Creaming the butter and sugar thoroughly at the start of the recipe and beating in the eggs carefully will also help to lighten the texture of the cake.