01 - Combine warm milk, 1 tablespoon sugar, and yeast in a large mixing bowl. Let sit for 5 to 10 minutes until foamy.
02 - Add remaining sugar, eggs, softened butter, vanilla, salt, and lemon zest to the yeast mixture. Mix until well combined.
03 - Gradually mix in flour until a soft dough forms. Knead by hand or with a mixer for 8 to 10 minutes until smooth and elastic.
04 - Place dough in a greased bowl, cover loosely, and let rise in a warm place for 1 to 1.5 hours until doubled in size.
05 - Mix softened butter, brown sugar, and cinnamon into a smooth paste while dough rises.
06 - Punch down risen dough and roll out on a floured surface into a 10 by 20 inch rectangle.
07 - Spread cinnamon filling evenly over the dough, leaving a 1 inch border on all sides.
08 - Roll up the dough tightly from the long side and pinch the seam to seal completely.
09 - Shape the rolled dough into a ring and transfer to a parchment-lined baking sheet. Pinch the ends together to seal the circle.
10 - Cover loosely and let rise again for 45 to 60 minutes until noticeably puffy.
11 - Preheat oven to 350 degrees Fahrenheit. Bake for 30 to 35 minutes until golden brown.
12 - Let cool on a wire rack for 20 minutes before decorating.
13 - Whisk powdered sugar, vanilla, and enough milk together to achieve a thick drizzling consistency.
14 - Drizzle icing over the cooled cake and immediately sprinkle colored sugars in sections to create a festive appearance.