Heat the oven to 180C/160C fan/gas 4. Butter and line a 20cm cake tin. Beat together the butter and sugar using a hand whisk or freestanding mixer, for 5 mins until pale and fluffy. Beat in the vanilla and eggs, then fold through the flour, lemon zest and milk. Spoon the mixture into the tin, smooth over and bake for 18-20 mins until golden and firm to the touch. Leave to cool completely before starting the meringue.

Whisk the egg whites to stiff peaks in a clean bowl, then add the sugar 1 tbsp at a time while whisking continuously, until you have a thick, glossy mixture that holds its shape when the beaters are lifted away from the bowl. Quickly beat in the vinegar.

Remove the ice cream from the freezer 10 mins before you assemble to soften slightly. Place the sponge on a serving plate. Spread the jam over the top of the sponge in an even layer. Scoop balls of the ice cream into a mound in the middle of the sponge, leaving a 1-2cm gap of sponge around the edge. Gently smooth the side and top of the ice cream with a palette knife. Spoon and swirl the meringue around the outside of the ice cream and cake base with a large spoon. Use a blow torch to evenly brown the outside of the meringue, if you have one. Cut into wedges to serve.