For the raspberry coulis
- In a frying pan, off heat, add the raspberries, the sugar, and transfer over medium heat.
- Simmer for 3-4 minutes, by constantly mixing until they melt.
- Remove the mixture from the heat and set it aside to cool.
For the cake layers
- Preheat the oven to 180ο C (350ο F) set to fan.
- Separate the egg whites from the yolks.
- In a mixer’s bowl add the egg whites, half of the sugar, a pinch of salt, and beat with the whisk attachment at high speed until there is a meringue.
- Remove and set aside.
- Place the bowl on the mixer and add the yolks, the rest of the sugar, the vanilla extract, the lemon zest, and beat very well with the whisk attachment at high speed until the mixture is fluffy.
- As soon as the mixture with the egg yolks turns fluffy, keep beating, add the lemon juice, the flour slowly, a pinch of salt, the 1/4 of the meringue, and beat at high speed for 2-3 seconds.
- Add the meringue and mix softly with a spatula until there is a uniform mixture.
- Butter a 30x40 cm baking pan, spread parchment paper, and then spread the whole mixture.
- Bake for 15 minutes. Remove and let it cool well.
- Take the cake out of the baking pan, carefully remove the parchment paper, and cover with a kitchen towel. Drizzle the towel with a little water and fold the cake into a roll with the towel in between. Set aside.
For the buttercream frosting
- In a mixer’s bowl add the butter in pieces, the icing sugar, and beat well with the paddle attachment at high speed for 3-4 minutes until the buttercream is fluffy.
- Add the remaining coulis to the buttercream and beat with the paddle attachment for a few seconds. Then, add the coulis into the buttercream and beat with the paddle attachment for a few seconds. Then, remove the bowl and mix softly with a spatula.
- Unwrap the cake, remove the towel, and spread 2/3 of the buttercream over its surface. Spread half of the fresh berries all over. Keep the rest for serving.
- Cut three even strips on the shorter side of the cake. Wrap one strip into a roll and put it over the edge of the second strip. Roll them together and follow the same process with the third strip too, until there is one big roll.
- Spread the remaining buttercream over the whole surface and serve with the rest of the berries.