Take eggs and butter out of fridge, and let come to room temperature. Crumble saffron into 1/4 cp. boiling water and let stand. Warm cream (on extremely low heat in a saucepan). Grate the orange rind and lemon rind, reserving the lemon juice for the kringel dough. Into the 1/4 cp. of warm water mix the teaspoon of Sugar, and sprinkle yeast on top of water. Let stand (about 10 minutes) until bubbled up. In a large bowl, combine warm cream with yeast mixture and add half of the flour. Mix well. Cover and let rise for half an hour in a warm place.