Preheat the oven to 160°C/Gas Mark 3. Grease and line two 20cm (8in) sandwich tins with baking paper.
Break the eggs into a bowl and whisk with a fork to combine. Measure all the other ingredients except the jam into a large mixing bowl, add the eggs and beat until thoroughly combined. Divide the cake batter equally between the two prepared tins. Level the surface with the back of a spoon or spatula.
Bake on the middle shelf of the oven. Place both tins on the same shelf, one positioned at the back on one side of the oven and one positioned at the front on the other side of the oven. This ensures an even bake. Bake for 25-30 minutes, or until the edges of the cake shrink back from the side of the tin.
When cooked, remove from the oven and leave in the tin for a few minutes before turning out onto a wire rack to cool completely.
When completely cold, sandwich the cakes together with the jam. Finish with a sprinkling of caster sugar on top.