- Grease and base line 2 x 20cm cake tins. Preheat the oven to 180C/fan 160C/ gas mark 4. Line a wire rack with a sheet of baking parchment.
- Place the egg yolks in a large bowl with 60g of the sugar and the salt and whisk it until becomes pale and thick enough to leave a trail across the top.
- In a separate bowl place the egg whites and whisk until they hold soft peaks - make sure you use clean whisks, any hint of grease will contaminate the whites and they won’t whisk up. Gradually add the remaining sugar whisking between additions to get a smooth and shiny meringue.
- Add a large spoonful of the meringue mix and stir into the yolk mixture to slacken it. Sprinkle over half the flour and very gently fold this in. Followed by half the meringue and then repeat with the remaining meringue and flour. Take it slowly - this stage takes time to achieve a smooth mixture and you need to be very careful not to knock out the air you have already incorporated.
- Combine the butter and vanilla and add this to the bowl. Carefully fold in until well combined. Divide the batter between the tins and bake for 20-25 minutes until golden and springy to touch. Remove from the oven, leave in the tin for a few minutes and then invert onto the wire rack to cool.
- Once the cakes are cool, slice each horizontally so you have 4 layers. Whip the cream with the lemon zest until it is soft and dollopy. Spread a quarter of the cream over one layer, add a quarter of the fruit and continue layering. Finish with a layer of cream and fruit on top. Store in the fridge for up to 24 hours.
Similar to our Victoria sponge in flavour, in a Viennese sponge the eggs are separated and given strength by creating a meringue with the whites before folding into the rest of the ingredients. The method is a little time consuming but the result is a light and delicious sponge which lends itself to layers of fruit of cream!