In a large bowl, whisk together flour, sugar, and instant yeast.
Ensure the buttermilk and butter are both warmed to a temperature between 110°F to 115°F.
Add the buttermilk and butter into the flour mixture and beat on slow speed with an electric mixer with a dough hook. Beat for about 30 seconds.
Add the eggs and salt into the mixture and beat on low speed for 3 minutes. Scrape down the sides of the bowl to ensure everything is well combined.
Place the dough in a lightly greased bowl, cover with a clean towel, and let rise in a warm place for 45-60 minutes.
Roll out the dough and spread the cinnamon sugar filling evenly. Fold and roll the dough, then twist it into a ring shape and place it on a baking sheet.
Let the dough rise for another 15-20 minutes.
Preheat the oven to 375°F.
Bake for 20-25 minutes or until golden brown.
While the cake cools, mix confectioners’ sugar, milk, lemon juice, and vanilla extract to create the glaze. Drizzle over the warm cake and top with colored sanding sugar.