Preheat the oven to 200c / gas 6.
Cut the Bramley apple into 1cm slices. In a small bowl, coat the apple slices with oil and arrange on a baking sheet lined with parchment paper. Season and bake for 5 minutes until soft but not collapsing. Remove from the oven and set aside.
Grease the tin liberally or spray with cake release spray.
Combine the flour, salt and sage in a medium bowl.
Whisk the eggs, milk, melted butter and cooked Bramley apple in a separate bowl.
Pour the wet ingredients over the flour and beat with a balloon whisk until blended and smooth-ish. Decant the batter to a jug. If you are worried the apple is too lumpy you can fix this with a very quick blitz with a stick blender.
Meanwhile pop the tin into the oven for a couple of minutes to heat it up.
Take the tin back out of the oven and quickly serve small pools of the batter into the tin and bake for 12-14 minutes until puffed up and golden brown. Don't open the oven during cooking but when you get them out give them a poke to see if they're cooked underneath.
Allow to cool slightly before removing from the tin and arranging upside down. Serve with additional baked Bramley apple slices on top.