Measure out the ingredients.Line the loaf tin with a cake liner. If a loaf liner is unavailable, rub butter on the inside of the cake pan and line the bottom and sides with parchment paper. Add baking powder to the self raising flour and mix. Set aside.
Add butter and sugar to a mixing bowl and use an electric mixer to mix it until it's light in colour and fluffy.
Break the eggs and add to the butter and sugar mix. Add vanilla extract and use the mixer to whisk it all together.
Add the flour, and use a spatula to mix then use the mixer on low speed to mix for 1 minute for all the ingredients to come together.
Pour the cake batter into the prepared loaf tin.
Bake Sponge loaf cake in the oven at 160C/360F for 45 minutes or until it's baked through inside. A skewer when inserted in the middle should come out dry.
Bring out the cake from the oven, let it cool in the pan for at least 5 minutes then turn it onto a wire rack to keep cooling.