Start by cooking the cherry jam if using home made. See note 1 for the one I made.
Preheat the oven to 175 degrees Celsius.
Line or grease a 16-18 cm spring form.
Add eggs and granulated sweetener to a bowl. Whisk until smooth, fluffy and the mixture has turned quite pale using an electric whisk.
Add mashed banana, apple sauce, 1 dl sour cream and vanilla drops. Stir/whisk until fully incorporated. Don't whisk for too long.
Combine the oat flour, corn flour, coconut flour, cinnamon, baking powder, baking soda and salt in a separate bowl.
Gently and little by little add the dry ingredients to the wet, stirring gently until combined. Don't stir too much.
Next combine the ingredients for the streusel in a bowl. If too dry add a little more apple sauce or coconut oil.
Pour the batter into the prepared spring form.
Dollop the cherry jam over the cake, then using a knife or skewer make swirls in the batter.
Dollop sour cream (1/2-1 dl) depending on how much you prefer. Make swirls using a knife or skewer.
Sprinkle the streusel over the cake and press gently down to make sure it sits after baking.
Bake in the middle of the oven for 36-42 minutes, until an inserted knife or skewer comes out clean.
Take out and let the cake cool before removing it from the spring form and cutting it.