Grease an 8-inch cake pan with butter and line the bottom with parchment paper.
Preheat the oven at 400℉ (200℃). If you’re using a fan-forced oven, lower the temperature by 20 degrees.
In a large mixing bowl, whip the butter, sugar and orange zest until light and fluffy. Add one egg at a time and whip to incorporate. Add the orange juice and vanilla essence, and mix well.
In another bowl, add the semolina, baking powder, ground almonds and cardamom powder. Mix well with a fork. Then slowly add the dry ingredients to the butter mix, and gently fold them in.
Pour the batter into the tin and even the top out with a small offset spatula. Place the thin slices of orange onto the top of the batter. Place it in the oven and lower the temperature to 355℉ (180℃).
While the cake is baking, bring ½ cup of orange juice and two tablespoons of sugar to a boil to make the syrup. Set aside.
Bake for 30 minutes or until your skewer comes out clean.
Remove the cake from the oven and pour syrup over it while it’s hot. Set it aside to cool down in the pan. After it’s cooled, loosen the sides with an offset spatula for easier removal. Serve immediately.