Preheat oven to 190°C/370°F and grease a springform pan (24 cm-diameter or 9 1/2 inch) with coconut oil.
Mix flax seeds with the warm water and keep aside to thicken.
In a mixing bowl mix coconut blossom sugar with melted coconut oil, vanilla and 2 tsp cinnamon. Add the flax seed mixture, lemon peel, coconut yoghurt, almond milk and ground almonds and mix.
Mix brown rice flour with corn starch and baking powder. Sift over the batter and mix. Spoon into the prepared springform pan.
Peel and core apples and cut them in quarters. Slice the tops without cutting all the way through. Mix together with lemon juice, remaining cinnamon and coconut blossom sugar. Place onto the batter, sprinkle with the almond slivers and keep in the oven.
Bake for 50-60 minutes on medium rack. Insert a toothpick to check if the cake is done. If it comes out clean the cake is ready. Let cool on a wire rack.