Get the oven and tin ready. Heat the oven to 160C (fan 140C, gas 3). Lightly grease a deep 20cm loose-bottomed cake tin.
Make the all-in-one batter. Put the flour, baking powder, caster sugar, eggs, almond extract and melted butter into a mixing bowl. Mix until everything is blended, then beat for one minute. The batter will be thick and smooth, with no pockets of dry flour.
Lay down the base. Spread half of the batter over the bottom of the prepared tin, pushing it out to the edges in an even layer.
Add the apples. Cut the apples into thick slices and arrange them over the batter, heaping most of them in the centre. This stops the fruit from breaking through the sides once the batter spreads.
Cover with the rest of the batter. With two dessert spoons, drop the remaining batter over the apples in rough spoonfuls. Focus on covering the centre well. It will look uneven, but the batter spreads out as it bakes.
Scatter the almonds. Sprinkle the flaked almonds evenly over the top of the cake.
Bake low and slow. Bake in the preheated oven for 1¼ to 1½ hours. It’s ready when the top is golden and the cake has begun to shrink away from the sides of the tin.