Preheat the oven to 175 degrees Celsius. Line or grease a spring form.
Combine almond flour, tapioca flour, salt, baking powder, baking soda and poppy seeds in a bowl.
Whisk eggs together with granulated sweetener until slightly fluffy in a bowl.
Add milk, stevia drops, liquid sweetener, apple cider vinegar and lemon zest to the mixture and whisk to combine.
Add the dry ingredients to the bowl and blend until incorporated and smooth.
Pour the batter into the lined spring form.
Arrange plums on top in circles.
Sprinkle slivered almonds on top.
Bake in the middle of the oven for 25-30 minutes. Check using a toothpick if it comes out clean.
Let the cake cool before cutting and serving.