Pre-heat oven to 180°C (convention)/160°C (fan-forced/convection).
Place spelt flour, desiccated coconut, baking powder and salt in a medium bowl. Toss to combine.
Place rapadura sugar, eggs, vanilla, cinnamon, allspice and lemon zest in the bowl of an electric mixer and mix for a couple of minutes until light and fluffy. Add butter and mix briefly until well combined and smooth.
Add the dry mix to the wet mixture and mix gently by hand, using a wooden spoon until just combined.
Grease a 25-27cm fluted ceramic pie/flan dish with melted butter. Dust with desiccated coconut and tap and turn the pan to coat evenly. Shake off excess coconut.
Gently spoon the cake batter into the prepared pan. Arrange apple slices in a circular fashion starting from the outer edge, making sure the slices slightly overlap each other.
Dust the cake and apple slices with cinnamon sugar. Bake in the pre-heated oven for 35 minutes until browning and cooked through.
Remove from oven and cool slightly. Dust with icing sugar. Cut into wedges and serve with a dollop of vanilla ice cream.