1. Preheat the convection oven. 2. Remove the pits from the peeled pears and cut them into pieces of the same size. Mix with lemon juice and 150 g of sugar. We can also add a little ground cinnamon. Then put it in the baking dish. 3. Prepare the crumble. Either in a machine or by hand, knead the flour, butter, sugar and chopped walnuts. Spread evenly over the pears and place in the convection oven. 4. Bake until golden brown for about 25 minutes. Serve as soon as possible after baking, preferably with vanilla cream or ice cream.