Grease a 27cm (10 inch) bundt pan.
Pre-heat the oven to 180°C, 160°C fan, 350°F, gas mark 4.
Mix the all the wet ingredients (brown sugar, olive oil, eggs, vanilla, apple sauce, milk, apple cider vinegar) together in a large bowl.
In a separate large mixing bowl whisk together the dry ingredients (buckwheat flour, sorghum flour, cassava flour, baking powder, bicarbonate of soda, spices, salt).
Add the dry ingredients into the wet ingredients and mix well by hand or using an electric mixer until smooth.
Pour the cake mixture into the bundt pan, smooth the surface with a rubber spatula and bake in the oven.
for 40-45 until an inserted cocktail stick comes out clean.
Remove the cake from the oven and rest for 5 minutes before inserting the cake out of the bundt pan.
Cool completely on a wire rack before frosting.