Grease a tart pan thickly with 25 g butter and sprinkle with 25 g sugar.
Peel, quarter and core the pears. Drizzle with lemon juice.
Place in the tart pan with the curve facing down. Scatter the finely chopped walnuts in the spaces between them and on the pears.
Mix in the remaining butter and sugar (150 g each) until frothy, gradually stir in the eggs. Finally, fold in the flour and stir everything into a smooth dough. Pour the batter into the tart pan.
Bake for 45 minutes. Let cool down for 10 minutes.
Place a cake plate on the tart pan and turn the tart out onto it.