Peel and chop two apples, then blend into a smooth puree
In a large bowl, combine the apple puree with oat flakes and eggs
Stir in 1 tbsp of baking powder until fully incorporated
Line a 18 cm (7 inch) tin with parchment paper, including the sides
Pour the oat-apple mix into the tin and spread evenly
Decorate the top with cranberries and walnuts
Heat the oven to 180°C (356°F)
Bake for 40–45 minutes until golden and firm
Let the pie cool in the tin for 15 minutes, then transfer to a rack
Serve warm or refrigerate for later