German Plum Cake aka Zweschgendatschi

This is the foundation of the flat German cake I grew up making. My stepmother Gisela taught me this. She's been gone over 20 years but I think about her every time I make a kuchen in this style. 
You can use plums, apples, peaches, blueberries...they all work. You can put a crumb top on it too. But fundamentally the recipe is:
2 cups flour
2 tsp baking powder
.25 tsp salt
1 stick, 4 ounces butter-melted
2 eggs  
1 cup sugar 
3 pounds of fruit. A little less for berries because they don't have cores or stones.
3 tablespoons sugar or crumble topping. (Look that up later)

350 oven 
In a stand mixer combine flour, baking powder and salt. Mix. Dump in everything else but the fruit. Mix til well combined maybe 2 minutes. It will be soft. Press into a well oiled 14x17 inch pan (or go with a smaller pan for a thicker crust. Arrange the fruit neatly and sprinkle with sugar. Bake 40-60 minutes, depending on how juicy your fruit is. Look for the dough between the fruit to be dry(ish) or for it not to stick to your finger when you touch it. Cool. This cake is typically better 12 to 24 hours after it has been made.