Preheat the oven to 350 degrees f.
Prepare the pan. Cut out a circle of parchment paper to fit in the bottom of the pan. Spray the pan with non-stick cooking spray. Place the circle of parchment paper in the bottom of the pan and spray that as well. Set aside.
Cut the butter into approximately tablespoon pieces and place it in a microwave safe dish. Melt in the microwave about 30 seconds. It does not have to be 100% melted. Set aside.
Zest the orange.
Add the sugar to a small bowl.
Combine the orange zest and sugar, rubbing the zest and sugar between your fingers. Set aside.
Sift the almond flour into a medium bowl. Add the cardamom and gently stir to combine.
Add the butter and orange zest/sugar mixture to the bowl of a stand mixer fitted with a paddle attachment. You can mix this cake by hand if necessary.
Mix on low speed until combined, about 2 minutes.
Add the eggs and almond extract and mix on low until combined.
Gently pour the almond and cardamom into the butter and sugar. Mix on low until just combined.
Mix in the Greek yogurt, mixing on low until just combined. Do not over mix.
Pour the batter into the prepared pan.
Evenly sprinkle the top of the cake with sliced almonds.
Place in the preheated oven and bake until the edges pull away from the sides and a knife or wooden skewer inserted into the middle comes out clean, about 45 minutes.
Allow to cool completely before removing from the pan.
If you wish to decorate with confectioners sugar, place a small amount of the sugar into a fine mesh sieve. Hold the sieve over the cake and gently tap on the side adding a light dusting of the sugar.