Put the 7 clementines for the cake in a small pan and cover with water (they will bob to the top). Cover and bring to the boil, then turn down the heat and simmer for about 1.5 to 2 hours, turning once, until soft. Alternatively, you can microwave them on high until soft.
Drain and allow to cool slightly, then cut open to check for pips, removing any you find, and puree the fruit.
Heat the oven to 350°F, and grease and line a 9-inch springform pan.
Beat together the egg yolks, sugar, and honey until thick and pale, then fold in the ground almonds, followed by the clementine puree and soaked saffron until well combined.
Whisk the egg whites and salt until stiff peaks form, then gradually fold into the batter, being careful to knock as little air out as possible. Spoon into the tin and bake for about 45 to 50 minutes, or until firm on top.