For the jam, cook 400g of the berries with the sugar and lemon zest and juice in a semi-covered medium saucepan over medium heat, stirring occasionally, for 5 minutes, to soften the berries and dissolve the sugar.

Gently simmer, without stirring, for 30-40 minutes, until thick and glossy, then add the remaining 100g berries. Cook for a further 5 minutes, stirring occasionally, then test whether jam is ready by placing a teaspoon of jam onto a plate that’s been chilled in the freezer and tilting the plate – when the jam holds together and doesn’t slide down the plate, it’s ready. If it does slide down the plate, cook for a few more minutes, then test again.

Pour the hot jam into sterilised jars and seal the jars. Cool completely at room temperature (see recipe note).

To make the cakes, preheat oven to 200°C/180°C fan-forced.

Grease base and sides of 2 x 20cm round cake pans with extra butter. Place a little sugar on the inside edge of one cake pan and roll it around to evenly coat the whole inside edge. Pour the excess sugar into the other pan and repeat the process, adding more sugar if needed. Discard any remaining sugar.

Repeat the process with flour to coat each pan, then line bases of both pans with baking paper.

Sift the flour and baking powder three times (this will give you a lighter end result). Melt the butter with 3 tsp water in a small saucepan over low heat.

In a stand mixer fitted with the whisk attachment, whisk the eggs until pale and foamy. Add the sugar, one-third at a time, whisking after each addition. Once thick, pale and creamy, gently but quickly fold the flour and butter into the eggs, retaining as much air as possible. Divide the mixture between prepared pans and quickly place them in the oven. The quicker this process happens, the more air will remain in the batter. Bake for 25-30 minutes, until sponges spring back when gently pressed on the surface.

Remove pans from the oven and immediately invert the cakes onto a wire rack covered with a tea towel to cool completely.

Measure out 150g jam. On one of the cakes, spread jam across the surface and top the jam with the whipped cream. Place the dressed cake on a serving plate and top with the undressed sponge.

For the icing, mash thawed frozen berries with a fork. Strain through a fine sieve into a small bowl, discarding seeds. Place the sifted icing sugar in a medium bowl and add 2 tbs strained pulp. Stir until smooth and bright pink.

Spoon icing over cake, letting it drip drown the sides. Serve cake topped with fresh raspberries.