Combine egg whites and sugar in top of double boiler; cook, stirring constantly, over hot (not boiling) water, until sugar dissolves and egg whites are warm. Pour egg mixture into a large bowl; whip until stiff.
Put coconut in a separate large bowl. Cut vanilla bean in half lengthwise; scrape seeds, and add to coconut, stirring until blended. Stir in lemon rind and sour cream.
Fold egg white mixture into coconut mixture. Shape mixture into small mounds (1 1/2 inches in diameter) on a baking sheet lined with parchment paper.
Bake at 350° for 10 minutes or until macaroons just begin to brown. Cool completely on wire racks. Place macaroons on a serving plate. Garnish, if desired.
Note: Use a small ice-cream scoop to make evenly shaped cookies.