How to cook
Clean the pits from the plums and divide them into halves. Soak them in the rum and cinnamon for 30 minutes, stirring them occasionally. In a bowl, beat the butter and sugar until fluffy and add the eggs one at a time.
Mix in the vanilla, lemon zest and the juice of the drained plums. Sift flour with baking powder and gently mix it into the mixture with a spatula. Pour the mixture into a shape, covered with baking paper. Mix the brown sugar with the biscuit crumbs and sprinkle them with half of this mixture.
Arrange the prunes tightly and sprinkle on the remaining half of the biscuit mixture. Press down gently and place the pie with plums to bake in a preheated 340°F (170 °C) oven.
Before you serve it, let it cool.