Pre-heat oven to 175C/350F
Grease and line a 20cm/8 inch round cake tin.
Shift the dry ingredients together.
Purée the apple and pumpkin together.
Add the egg whites to the bowl of a kitchen stand fitted with a whisk attachment.
Whisk the egg whites until soft peaks from.
Slowly, add the Maple Syrup whilst whisking on medium/high.
Add the egg yolks and continue to whisk until combined.
Turn the mixer to low and add the pumpkin/apple purée.
Add the dry ingredients to the wet and whisk on low until combined.
Scrape down the sides of the bowl.
Whisk on medium/high for 1 minute.
Pour cake into prepared tin.
Bake for 45 minutes, or until cooked through.