Step 1
Mix orange juice water and cinnamon in a microwave-safe bowl. Heat in the microwave until the mixture registers 110 degrees F (43 degrees C) on an instant-read thermometer 1 to 2 minutes.
Step 2
Stir yeast into the orange juice mixture. Let stand until yeast is creamy and frothy about 45 minutes.
Step 3
Combine sugar and margarine in the bowl of a stand mixer. Beat until creamy. Add eggs; beat on high speed for 30 seconds. Mix in yeast mixture and orange zest until well combined.
Step 4
Sift flour salt and baking powder together in a bowl. Add gradually to the mixture in the stand mixer mixing with a bread hook until a soft sticky dough forms about 5 minutes.
Step 5
Transfer dough to a large glass bowl. Cover with plastic wrap; let rise in a warm place until doubled in size 2 to 4 hours.
Step 6
Preheat oven to 350 degrees F (175 degrees C). Grease 2 round cake pans.
Step 7
Divide dough into 2 equal pieces. Put 1 wrapped coin in each piece; knead for 2 to 3 minutes and shape into a ball. Place 1 ball of dough in each cake pan. Cover with plastic wrap; let rise until puffy 2 to 4 hours more.
Step 8
Whisk egg white and vanilla together in a small bowl. Brush over the top of dough.
Step 9
Bake in the preheated oven until a knife inserted into the center comes out with a few crumbs attached 30 to 55 minutes.