Wash, clean and quarter the plums, removing stones. Mix flour, baking powder, salt and sugar in a large mixing bowl. Whisk the eggs, oil, yoghurt, orange peel and 5 tablespoons of juice and stir with a spoon briefly into the flour until everything is just mixed (the dough should not be smooth).
Fold in plums. Place 2 paper cuffs in each well of a muffin tin (12 wells). Fill in the dough. Bake in a preheated oven (electric range: 175 °C/ convection oven: 150 °C/ gas: level 2) for 25-30 minutes until golden brown.
Let it cool down on a cake rack.