01 -
Preheat the oven to 350 ℉ and line and grease an 8 or 9 inch springform cake pan - can also use a regular cake pan.
02 -
In a large bowl, and with a handheld mixer or a whisk and a lot of arm strength, beat the sugar and egg yolks until light and foamy. Add the orange zest, orange juice, oil, and almond extract and whisk for about two more minutes until well incorporated.
03 -
Add the almond flour and baking powder, and mix until combined. The mix should be smooth without any lumps.
04 -
In a large clean bowl, beat the egg whites until firm peaks form. Carefully fold into the cake batter. Note: If the bowl is greasy or if your egg whites had a bit of egg yolk, they will not foam up at all. Make sure your bowl and beaters are clean and wiped with vinegar prior to mixing.
05 -
Pour into the prepared pan, evenly spreading the top across the pan. Sprinkle the sliced almonds over the top. Bake for about 40 minutes, until golden or until a toothpick inserted in the middle comes out almost clean with just a few crumbs.
06 -
Let cool in the pan for 10 minutes before remove from the pan. If you used a regular cake pan, invert the wire rack over the cake pan, hold it tightly, and quickly turn it over to release the cake and place the inverted serving dish over the cake and invert again, leaving the cake up right onto the serving dish. Sieve powdered sugar on top to decorate and serve.