Preheat the oven to 180 degrees C. Grease the bottom and sides of two 20cm/8in sandwich tins, line the bases with greaseproof paper, and dust the sides lightly with flour.
Beat the butter and sugar together, until very light and fluffy.
Add the eggs one at a time, beating each one in well before you add the next, then fold in the flour and lemon zest.
Divide the cake mix between the prepared tins and bake for around 20 minutes until lightly golden brown and risen. Allow the cakes to cool slightly before carefully turning them out onto a wire rack to cool completely.
Meanwhile, gently warm the jam in a pan, remove from the heat and stir in the strawberries.
Whip the cream with the sugar, lemon juice and vanilla seeds until you have nice soft peaks.
Smear the jam and strawberries over the bottom cake, then spread the sweetened cream over the top. Place the second cake on top of the jam and cream layers and dust with icing sugar.
