Preheat the oven to 170°C and place rack into the centre of the oven. Butter and line the base of a 21cm cake tin or similar capacity square tin.
Place eggs and sugar into the Thermomix bowl and whip 8 min/37°C/butterfly/speed 3/MC off.
Add half the flour and salt to the Thermomix bowl and incorporate 6 sec/Interval/dough setting.
Pour in the melted butter then add the second half of the flour. Incorporate 10 sec/Interval/dough setting. Finish combining by gently folding with a silicone spatula.
Pour batter into prepared tin and bake 25–30 minutes or until golden and springing back when touched in the centre.
Cool sponge in tin on a cooling rack until completely cold. Remove from tin and cut into cubes.
Meanwhile make the Lemon Butter and when you are ready to assemble, whip the cream with plenty of vanilla bean paste to taste.
To assemble, dollop the bottom of your serving bowl with plenty of the whipped cream. Add spoonfuls of the cold lemon butter and a few sponge cubes, then lastly a few blueberries.
Repeat this process until all the cake is used. You will need it all. Refrigerate until serving.