For the crumble, quickly knead butter, flour, sugar, vanilla, salt and lemon zest, wrap in foil and refrigerate for 1 hour.
Separate eggs into yolks and clear. Cream butter with salt, powdered sugar, vanilla and lemon zest until very fluffy, add yolks one at a time and continue to beat until creamy.
Beat egg whites with granulated sugar until creamy. Stir the nut-flour mixture into the butter mixture, stir in 1/3 whipped cream well, fold in 2/3 whipped cream.
Fill the mixture into a 20×30 buttered baking dish, spread smooth and sprinkle with blueberries. Grate the cooled crumble mixture onto the blueberries with a coarse grater. Bake in the oven on the middle shelf at 170° for 45 minutes.