Preheat the oven to 190°C. Lightly grease a 4-cup capacity ovenproof dish.
Add the sultanas or raisins to the hot apples and place in the prepared dish.
Place the flour, baking powder, cinnamon, brown sugar and rolled oats in a food processor and process for 10 seconds. Add the butter and process until the mixture resembles coarse breadcrumbs. Stir through the sunflower seeds if using.
Spoon the crumble mixture over the apple mixture and place in the oven. Cook for 20-25 minutes until golden and bubbling.
Serve crumble with Puhoi Valley Vanilla Bean Custard.