Line an 8 inch round spring form pan with parchment paper.
Preheat the oven to 375°F
In a large bowl, combine the sorghum flour, almond flour, buckwheat flour, icing sugar, baking powder, apple pie spice and salt
In a medium bowl cream the butter, white sugar and brown sugar for about 2 minutes, or until it is smooth and lighter in colour. Then beat in the egg until it is just mixed.
In a smedium bowl add the milk, honey, and lemon juice. Whisk in the psyllium and flax seed, then let it sit and gel while slicing the apples.
Wash, core and thinly slice the apples with a mandolin or a sharp knife.
Add the psyllium husk mixture to the creamed butter and sugar. Stir it in until just combined, and then with a spatula, pour the wet ingredients into the dry ingredients. Mix until there is no loose flour.
Pour the cake batter into the prepared pan, and place the sliced apples over the top.
Bake for 35 minutes, or until a toothpick comes out clean. Let the cake cool for about 15 minutes before removing it from the pan and before slicing.
Enjoy while the cake is still warm, but it is equally delicious cold. If there are any leftovers, store them covered in the refrigerator for up to 4 days.