Preheat the oven to 140°C. Line a 22.5cm diameter x 4.5cm deep round baking tin with baking paper. Set aside.

Add all the dry ingredients, oat flour, almond meal, buckwheat flour, sugar, cacao powder, orange zest, salt to a medium bowl, mix and set aside.

Slice the orange into 3mm thick round pieces, use a mandoline slicer if available. Add orange and water to a small saucepan and bring to boil, simmer on low heat for 5 minutes. Carefully layer the orange slices onto the baking tin.

Use the same saucepan in (3), add orange juice and bring to boil. Pour the hot orange juice into a large bowl, then add oil, apple cider vinegar and whisk until combined.

To form the cake batter, add dry ingredients into wet ingredients and mix immediately until just combined. Be careful not to over mix.

Pour the mixture over the orange and bake for 60-70 minutes or until cooked when tested with a skewer.

Once cooked, leave in the baking tin for 10 minutes before flipping upside down onto a cake rack to cool.

Add orange juice and sugar to a saucepan on low heat, stir until the sugar has dissolved. Then bring to a boil and allow to bubble for 2 minutes.

Turn off the stove, stir in coconut cream to form the caramel. Allow to cool and thicken.