Preheat your oven to 375°F (190°C) and grease a 9-inch round cake pan or line it with parchment paper.
In a large bowl, whisk together the flour, granulated sugar, baking powder, and salt.
In a separate bowl, combine the milk, melted butter, and egg. Mix well.
Pour the wet ingredients into the dry ingredients and stir until just combined. Do not overmix.
On a floured surface, roll out the dough into a rectangle about 1/4 inch thick.
Spread the softened butter for the filling evenly over the dough.
In a small bowl, mix together the cinnamon and brown sugar, then sprinkle this mixture evenly over the buttered dough.
Starting from one long side, carefully roll the dough into a tight log. Pinch the seam to seal.
Cut the log into 8 equal pieces and place them in the prepared pan, cut side up.
Bake for 20-25 minutes, or until golden brown.
While the rolls are baking, prepare the glaze by mixing the powdered sugar and milk until smooth.
Once the rolls are done, let them cool for a few minutes before drizzling the glaze over the top.