Heat oven to 350°F (180°C). Whisk sugar and butter in a bowl. Add salt and eggs and whisk again.
Add flour and baking powder; mix well.
Sprinkle lightly with butter the baking form and place dough.
Cover the dough with plum halves skin side up on top but, instead, you can use plum jam. Sprinkle with mixture of sugar and cinnamon, depending on how much you like cinnamon or sugar. Bake 1 hour, approximately. Enjoy your meal!!!