Preheat the oven to 190ºC/170°C Fan (375ºF / 345°F fan-forced). Mist an 8 inch springform pan with cake release and line the bottom with baking paper. If you like, you can line the cake pan with thin citrus slices as I have done, but it’s not necessary.
Place the fruit in a microwave-safe container with a lid (ideally one with a vent). Pour water to almost cover them and pierce each fruit with a knife. Cook for 10 minutes or until the clementines are soft all the way through.
Sift the ground almonds and baking powder into the bowl and stir or beat to combine until the batter is smooth. Carefully pour the batter in the prepared cake pan and tap gently on the counter to release air bubbles. Bake for approximately 50 minutes, or up to an hour until the cake feels firm to the touch.
Run a knife around the edge of the cake pan to release the sides before carefully opening the spring form pan. Carefully invert onto a wire rack (this cake is quite fragile as it contains no gluten). Brush the cake with some marmalade to add a shiny glaze before serving.