Preheat the oven to 180 celsius (350 Fahrenheit) and grease a 23cm (9 inch) cake tin and line the base and sides with baking paper.
Begin by making the caramel for the topping. Place the sugar and water in a small saucepan and stir well. Place over a medium high heat and bring to a boil. Let the sugar bubble away until it turns a pale golden and remove from the heat and add the butter. Stir well until all the butter is incorporated and pour into the base of the prepared cake tin. Top with orange slices, making sure to fill in any gaps with pieces of orange trimmed to size.
In the bowl of an electric mixer cream the butter and sugar until pale and fluffy, around 10 minutes. Add the eggs, one at a time, beating well in between each addition, until well combined. Place the flour, baking soda, baking powder, cardamom and ground almonds in a bowl and stir to combine. Switch the mixer to it's slowest speed and add half the flour mixture along with half the yoghurt. When combined add the remaining flour mixture and yoghurt and beat until the mixture just comes together.
Carefully spread the cake mixture over the top of the oranges and smooth the top. Bake for 1 hour, then loosely cover with foil, and bake for a further 15 to 20 minutes, or until cooked. Remove from the oven and place on a cooling rack to cool for 20 minutes before removing the cake from the tin.