Put unpeeled clementines and lime in a pot with cold water cover with a lid, bring to a boil and cook until soft, about 1 and 1/2 hours. Check every now and again to ensure it doesn't boil dry
Drain and when cool, cut clementines and lime into quarters and add the stem ginger. Blitz the lot - skins, pith and fruit - with a hand blender or food processor
Pre-heat oven to 180c/gas mark 4. Grease and line the base of a 9-inch spring-form tin
Whisk the eggs and sugar in a bowl until thick and creamy
Fold in the almonds and baking powder and add the clementine purée and vanilla. Mix well but gently
Pour cake mixture into prepared pan and bake for an hour to an hour and a half, test with a skewer - if it comes out clean, the cake is ready. You may need to cover the cake with foil after about 60 minutes to stop the top from getting too dark
Remove from oven and leave to cool, on a rack, Leave in the tin until cold