Heat the oven to 190 degrees. Place a piece of baking paper on the rack. Put the amaretti cookies in a plastic bag and crush them with a rolling pin or the like. Place them in a bowl.
Cut the plums into two or four depending on their size. Melt two tablespoons of butter in a large pan (with a lid). Put in the plums and sprinkle with sugar. Add the lemon zest and juice and shake the pan a little on the heat. Let it cook for two minutes without the lid and two minutes with the lid on. If the plums are not fully ripe, they will need a little longer. You may need a little more lemon juice from the other half of the lemon and a little extra sugar if it needs to cook longer.
Carefully pour the plums (they are very hot) into the baking dish. Sprinkle a few tablespoons of amaretti crumble over the plums.
Use a mixer and mix the flour and baking powder in a bowl. Add butter in small pieces and mix until the consistency is like small oatmeal flakes. If you don’t want to use a mixer, rub the butter into the flour with your hands. Add sugar and mix with a fork. Then add the rest of the amaretti crumbs.
Spread the coating over the plums and make sure it covers well, all the way to the edges.
Place the mold in the oven on baking paper and bake for about 30 minutes. A little red juice should be bubbling and the top should be golden. Leave for 10-15 minutes before serving with ice cream, whipped cream or mascarpone.
You can use any type of plum or other fruit. You can also use berries.