In a small saucepan, combine the butter, sugar, cinnamon, cloves, and cognac for the syrup.
Heat gently until the butter melts (do not let it boil). Remove from heat and set aside.
In a large bowl, beat the cake's butter and sugar with a hand mixer until combined. Add the eggs one at a time, continuing to beat.
Add the vanilla and orange zest.
Mix the milk with the orange juice in a small cup, then add to the batter.
Add the flour and beat well until you have a smooth, even cake batter.
Peel the apples, cut them into thick rings, and remove the core to create a hole in the center of each ring.
In a round baking pan, pour the syrup first, then arrange the apple rings evenly on top.
Place a walnut in the hole of each apple ring.
Spread the cake batter evenly over the apples.
Bake in a preheated oven (top and bottom heat, not fan) at 180°C (356°F) for 45 minutes.
Invert onto a large serving plate and serve.