Place clementines in a pot with cold water to cover, bring to a boil, and cook for 2 hours.
Drain and, when cool, cut each clementine in half and remove the seeds.
Finely chop the skins, pith, and fruit in the processor (or by hand, of course).
Preheat the oven to 375° F.
Butter and line an 8-inch springform pan with parchment paper.
Beat the eggs. Add the sugar, almonds, and baking powder.
Mix well, adding the chopped clementines.
Pour the cake mixture into the prepared pan.
Bake for 40 minutes, cover with foil, and bake for an additional 20 minutes, or until a skewer comes out clean.
Remove from oven and leave to cool on a cooling rack.