Heat oven to 180C/160C fan/gas 4. Butter and line the bases of three 23cm cake tins. Cream the butter and sugar until light and fluffy, then add the almond extract and lemon zest. Use a fork to whisk the yogurt with the eggs. With the mixer on a low speed, add the flour, ground almonds and 1/2 tsp salt to the butter and sugar, alternating with the yogurt and eggs.
Divide the batter between the tins and bake for 35-40 mins or until a skewer inserted into the middle comes out clean. Cool in the tins for 5 mins, then turn out onto a wire rack, remove the parchment and leave to cool.
Beat the mascarpone to loosen it. Whip the cream until it holds its shape. Combine the cream, mascarpone and lemon juice, then carefully add the icing sugar and flower water to taste.
Assemble the cake just before serving. Toss the berries with the caster sugar. Spread the flattest cake with half the cream, then add half the fruit. Top with a second cake, spread with the rest of the cream and top with the rest of the fruit. Finish with the last cake, sift over icing sugar, then decorate with rose geranium petals and rose geranium leaves (as long as they’re small).