Preheat the oven to 175 degrees Celsius.
Grease a Bundt cake pan and set aside.
Melt the coconut oil and let it cool for 1-2 minutes.
Add eggs and stevia sugar to a bowl and whisk until a little fluffy.
Add the Greek yogurt/quark, apple sauce and coconut oil and mix until combined.
Combine the rest of the ingredients except for the plum jam in a bowl and stir to combine.
Add the dry ingredients to the wet stirring constantly. Mix until you have a smooth batter.
Either place a thin layer of the batter at the bottom of the Bundt pan and then add the plum jam on top if you want to have the jam at the top of the cake. Or add about 1/3 of the batter to the Bundt form and then add the plum jam in an even layer if you prefer to have the jam in the middle. Cover with the rest of the batter and bake in the oven for 25-35 minutes, until an inserted toothpick comes out clean.
Take out of the oven and let it cool completely before removing it from the pan.
Drizzle icing sugar on top (if using).