Line or grease a 20 cm spring form.
Preheat the oven to 175 degrees Celsius.
Add stevia granulated sugar, apple sauce, yogurt, fiber syrup to a blender and mix.
Add eggs, one by one and mix in between until incorporated.
Combine the dry ingredients in a separate bowl and combine.
Add the dry ingredients little by little to the wet and stir to combine.
When you have a smooth batter add the chopped walnuts and stir to incorporate.
Bake in the middle of the oven for 25-35 minutes. Insert a toothpick or knife to check so it comes out clean.
Take out the cake from the oven and let it cool completely before removing it from the spring form.
Meanwhile prepare the frosting by adding cream cheese, Greek yogurt, sugar, lemon juice and fiber syrup, honey or agave to a bowl and mixing using a hand mixer until combined and creamy. Place in the fridge until ready to frost the cake.
When the cake has cooled add the frosting on top and top with walnuts and drizzle more fiber syrup/honey/agave on top (if using).