Preheat the oven to 170°C and line a 20cm cake pan with non-stick paper.
To prepare the orange, first finely grate the zest. Next, remove all of the remaining skin and pith, and slice the flesh into rounds.
Using an electric mixer, beat the butter and sugar until light and fluffy. Add the eggs, one at a time, beating between additions. Add the vanilla, spices and orange zest, and stir through. Add the orange juice, flour and almond meal, and mix until just combined.
Lay the sliced orange on the bottom of the cake pan, and top with the cake batter. Place in the oven for 40-45 minutes, or until cooked through.
Whilst the cake is cooking, make the syrup by combining the sugar and orange juice in a small saucepan. Simmer over medium heat for 15 minutes, or until the amount of liquid has halved.
When the cake is cooked, pierce the top with a skewer many times, and pour the hot syrup over the cake. Allow the syrup to soak through for 10 minutes, before flipping the cake onto a serving plate. Serves 10-12.