Plum Crumble Cake

Autumn time is harvest time. When I am at my fathers house I use to help him harvesting the plums from the trees in the garden. We put up a ladder to reach the ones we can't pick from the ground. Sometimes the leaves are wet from the rain and it's misty around the garden. The plums are quite sweet and tasty. He uses to make jam out of them. This year I am not home for harvesting plums by myself.
Still I wanted to bake a plumcake,

so here is the recipe:
Beat 1 egg, 80 g butter, 80 sugar and a little bot of vanilla sugar until the mixture is fluffy.
Add 200 g flour and half a teaspoon baking powder.
To make the dough softer add 4 spoons of milk and 2 spoons of rum.
Put the dough in a form and place the cutted plums without the pit on it.
For the crumble (streusel) mix cold butter, flour, sugar and cinnamon, the mixture will crumble by itself if you are lucky. Sprinkle the streusel over the cake and put it in the oven for about 40 minutes. I did in a gas stove, so I can't give any exact information about the heat. In general I use to improvise a lot when I cook or bake.