Your cake might be dry if you add too much flour. I like to measure my flour using a kitchen scale so that I know exactly how much I am using. If you don't have a kitchen scale, check out how to measure correctly. Another reason your cake might be too dry is if you bake it for too long. Be sure to keep an eye on the cake, since it is in the oven for so long. Test it with a cake skewer after 60 minutes to see if it is done. If not, let it go for just another 2-3 minutes and check again.