Step by step

1. Place the sugar and eggs in a large heatproof bowl. Place the bowl over a pan of simmering water, make sure the bottom of the bowl does not touch the water. Start mixing on the lowest speed and gradually increase to speed 6. Mix for at least 8-10 minutes until the mixture turns pale, thick and has significantly increased in volume.

2. Remove bowl from the pan. Add sifted flour into the bowl and fold into the mixture.

3. Add about 50 g of the mixture to the butter and mix throughly. Transfer back to the bowl.

4. Preheat the oven to 190°C. Line 2 round cake tins with parchment paper. Divide the batter between the cake tins. Smooth out and bake for 20-25 minutes. Let cool off in the tin for 10 minutes. Remove from the cake tin and cool the cakes completely. Use the sponge as a base for layered cakes.