Grease and line 2 x 20cm sandwich tins: use a piece of baking or silicone paper to rub a little baking spread or butter around the inside of the tins sponge cake mix the sides and base are lightly coated. Line the bottom of the tins with a circle of baking paper. Break the eggs into a large mixing bowl, then add the sugar, flour, baking powder and soft butter. Mix everything together until well combined.
Divide the mixture evenly between the tins. Use a spatula to remove all of the mixture from the bowl and gently smooth the surface of the cakes. Place the tins on the middle shelf of the oven and bake for 25 minutes. Don’t be tempted to open the door while they’re cooking, but after 20 minutes do look through the door to check them. While the cakes are cooking, make the jam.