This is the one I make, never had a failure yet.
6 ozs self raising flour
6 ozs margarine
6 ozs sugar
3eggs
1and a half teaspoons of baking powder.
Slightly beat the eggs then put everything into a mixing bowl and with a mixer beat for about 2 minutes, takes a lot longer by hand. Divide the mixture into two 8" tins, I always weigh the tins with the mixture in so as to get two equal size sponges. Bake in a preheated oven at 350 degrees F or 180 degree C for about 25 - 30 minutes. Sandwich together with jam or butter cream.
Treat yourself to the book Fast Cakes by Mary Berry