Grease a dish with butter 

Heat oven around 400 degrees depending on the setting of your oven

Whisk flour, a few tsp sugar, salt, baking powder and 5 tsps butter and mix

In a separate bowl mix milk, vanilla and egg. You can use Almond milk as well

Blend the milk mixture into the flour mixture slowly 

Mix well until smooth

Spread the mixture on the bottom of the baking dish

Spread the plum slices over the flour mixture in the baking dish

Spread the remaining sugar on the plums

Spread the remaining butter (melted) over the plums

Bake until it looks ready - should take less than 30 minutes