In a small bowl using an electric hand mixer on high, beat egg yolks, sugar and salt until thick and lemon colored - about a minute.On low speed, stir in sour cream, vanilla, zests & flour.Stir in enough additional flour to form a mass (1-2 tablespoons)Transfer to a floured surface and knead 50 turns (about 2 minutes), adding extra flour as needed.Divide dough in half, keeping extra covered with plastic.On a floured surface, roll each section paper-thin to at least 12” across. Cut into 1 1/4-inch strips. Cut strips into 5-inch lengths. Make a slit in each strip. Pull one end through slit to make a bow tie.Deep fry in oil at about 350-365° F for about 30 seconds, turning once using 2 forks, until lightly golden on both sides. Do not crowd.Drain on paper towels. Let cool an sprinkle with powdered sugar.To re-crisp place on baking sheet in a 325° oven for about 5 minutes. Cool completely and re-dust with fresh powdered sugar.