Combine flour, baking powder and salt, add to eggs. Stir with a wooden spoon, but do not overmix. Stir in vanilla and rind. Dough should be smooth and soft. Cut with a glass.
Drop doughnuts in, and fry until brown, turning once.
Drain on paper towels, then sprinkle with sugar. Let stand a while, then mix in flour and rest of ingredients. Roll dough in two parts. On one, cut with a glass. Place a little jam in the center of each.