Preheat the oven to 350 degrees F/175 degrees C. Grease and line a 9-inch/23-cm springform pan. Beat the yolks and sugar until light and pale. Beat in the cornstarch and corn flour until smooth. Beat in the pumpkin, rum and orange zest. Finally, in another bowl, beat the whites into peaks. Stir some of the whites into the pumpkin mixture to lighten it, then fold in the remaining whites. Pour the batter into the pan and bake until done, 45 minutes to 1 hour. Let the cake cool slightly before running a knife around the edges of the pan and removing the sides. Serve slightly warm (not too warm, or impossible to cut) with cinnamon whipped cream.