1. Preheat oven to 375 degrees Fahrenhait.
2. Place the plums in a casserole dish.
3. Squeeze the juice of one lemon over the plums.
4. Sprinkle the amaretto on top.
5. For the crumble: In a bowl, mix flour, brown sugar, salted cashews and mix it together.
6. Add the butter to it and mix into a crumble.
7. Sprinkle the curmble evenly over the plums.
8. Pop into the oven for 25 minutes.
9. Cut out a piece, plate, add a dollop of whipped cream on top and serve as dessert.