125 grams unsalted butter, cubed then softened
125 grams superfine granulated sugar
3 medium eggs, at room temperature, lightly beaten together
1 teaspoon pure vanilla extract
200 grams plain flour
2 teaspoons baking powder
2 tablespoons milk
6-7 apples cooking apples (granny smith or similar tart apple) peeled, cored and quartered
1 tablespoon superfine granulated sugar
1/4 teaspoon ground cinnamon
Put the softened butter in the bowl of an electric cake mixer and mix until soft and loose. Add the sugar, eggs and pure vanilla extract and beat until thick and creamy; don't worry too much if it separates - it all comes together in the end!
Sift the flour and baking powder together on to a piece of greaseproof paper, then mix in, a quarter at a time, adding the milk.
Transfer the mixture to a 9in round cake pan, the bottom and sides lined with parchment paper. Smooth the top of the batter. Partially slice the pieces of apple, about three-quarters of the way through each piece, open them up like fans and press them deeply into the cake batter; make two layers of apples. Mix the tablespoon of sugar and the cinnamon together and sprinkle the top of the cake with cinnamon sugar.
Bake in an oven preheated to (350°F) for 50 minutes, until golden brown. If the apples are still a little hard, cover the cake loosely with aluminum foil and continue cooking for 10 minutes more. Cool in the tin for 15 minutes, then turn out onto a plate. Serve warmish dusted with confectioners' sugar.