Put 100 g sugar into a cast iron tart mould or an ovenproof pan (25-26 cm Ø; no waffle base!) and caramelise over a low to medium heat on the stove until golden. Let the caramel cool down
Roughly chop the walnuts. Peel, quarter and core apples and cut them into approx. 1 cm thick slices. Then sprinkle with lemon juice
Cream 125 g butter, 125 g sugar, vanillin sugar and salt. Stir in the eggs one by one. Stir in flour first and milk at the end
Put 2 tablespoons of butter in flakes on the caramel. Sprinkle with the nuts. Place apple slices fan-shaped close together. Spread the dough on top and smooth it down. Bake in the preheated oven at the lowest level (electric oven: 200 °C/circulating air: 175 °C/gas: level 3) for approx. 40 minutes
Take it out of the oven. If necessary, to make it easier to remove the tart from the mould, heat on the stove over medium heat for 3-4 minutes. Remove the tart from the edge of the mould with a knife, turn it over and let it cool down. Served with: crème fraîche