01 - In a large mixing bowl, combine warm milk, 1 tablespoon sugar, and yeast. 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 add flour while mixing until a soft dough forms. Knead by hand or with a stand mixer for 8 to 10 minutes until the dough becomes smooth and elastic.
04 - Transfer dough to a greased bowl, cover with plastic wrap, and let rise in a warm place until doubled in size, approximately 1 to 1.5 hours.
05 - While dough rises, mix softened butter, packed brown sugar, and ground cinnamon into a paste until fully combined.
06 - Punch down the risen dough and roll out on a floured surface into a 10 by 20-inch rectangle with even thickness.
07 - Spread cinnamon filling evenly over the dough, leaving a 1-inch border around the edges. Roll up the dough tightly from the long side and pinch the seam to seal.
08 - Shape the rolled dough into a ring and transfer to a parchment-lined baking sheet. Pinch the ends together firmly to seal the circle.
09 - Cover the cake loosely with plastic wrap and let rise again for 45 to 60 minutes until visibly puffy and light.
10 - Preheat oven to 350°F. Bake the cake for 30 to 35 minutes until the exterior is golden brown and a wooden pick inserted into the thickest part comes out clean.
11 - Remove from oven and let cool on a wire rack for 20 minutes before applying icing.
12 - Whisk together powdered sugar, vanilla extract, and milk, adding milk gradually until the icing reaches a thick drizzling consistency.
13 - Drizzle icing over the cooled cake in decorative patterns. Immediately sprinkle colored sanding sugars in sections to create a festive appearance.