Prepare the oven: Preheat the oven to 180°C / 160°C fan / 350°F / Gas 4.
Line the tin: Line a 25 cm (10-inch) springform tin with baking parchment.
Cream the butter and sugar: Place the softened butter and caster sugar in a large mixing bowl, then beat until pale, light and fluffy.
Add the eggs: Add the eggs one at a time, mixing until just combined after each addition.
Add the milk and vanilla: Mix in the milk and vanilla until combined.
Add the dry ingredients: Sift in the flour, baking powder, fine sea salt and cinnamon, then fold until just combined and smooth.
Fill the tin: Spoon the batter into the prepared tin and level the surface.
Prepare the apples: Peel, halve and core the apples.
Arrange the apples: Thinly slice each apple half while keeping the slices together. Arrange them over the batter and press them in by approximately 1 cm (½ inch).
Add the honey: Spoon the honey evenly over the apples. Warm it briefly beforehand if necessary so that it pours easily.
Bake the cake: Bake for 45–50 minutes, until golden and a skewer inserted into the cake comes out clean.
Cool in the tin: Leave the cake to cool in the tin for 10 minutes.
Remove from the tin: Remove the outer ring and leave the cake to cool further.
Serve: Serve warm or cold, lightly dusted with icing sugar.