Gather the ingredients for the crumble. Into a food processor, add the flour, sugar, butter, eggs, baking powder, and a pinch of salt. Pulse until the ingredients are well-combined.
Place the crumble into the fridge while you prepare the plum filling.
Dice the plums into small cubes.
In a medium bowl, combine the plums, flour, sugar, and lemon juice.
Spread half of the crumbles onto a baking sheet (13in x 18in.), followed by a layer of plum filling.
Spread the remainder of the crumble over the plum filling.
Bake the plum crumble at 350°F for about 40 minutes or until golden brown.