Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan.
In a large bowl, cream together the butter and sugar until light and fluffy. Add the eggs one at a time, beating well after each addition. Mix in the sour cream and vanilla extract.
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt. Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
In a small bowl, mix together the cinnamon and sugar for the swirl.
Pour half of the batter into the prepared cake pan. Sprinkle the cinnamon-sugar mixture evenly over the batter. Pour the remaining batter on top and spread it out evenly.
Bake for 40 minutes, or until a toothpick inserted into the center comes out clean. Allow the cake to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.
In a small bowl, whisk together the powdered sugar, milk, and vanilla extract to make the glaze. Drizzle over the cooled cake.