Over medium heat in a small saucepan, melt butter. Do not brown it.
Preheat oven to 375 degrees.
Grease a 9-inch round cake pan and set aside. Line your pan with parchment paper. Almond cakes stick easily.
In a large bowl, beat the eggs.
Add the sugar and brown sugar. Combine with a whisk until uniform.
Add in the almond flour, baking powder, and salt. Whisk until combined. Don't overmix: Combine ingredients gently to keep the texture tender.
Add the orange zest and melted butter to the batter. Whisk the batter to incorporate the fat and the zest evenly, about 1 minute.
Pour cake batter into prepared cake pan and place in the preheated oven on middle rack for 40-45 minutes.
Take the cake out when it no longer has any jiggle in the middle and a toothpick comes out clean.
Let the cake cool for about 10 minutes before turning out onto a cake plate.
When the cake has completely cooled, top with room-temperature mascarpone or crème fraiche or other icing, and dust with powdered sugar or more orange zest.
