Preheat your oven to 350°F (175°C). Grease your bundt pan well to prevent sticking.

In a small bowl, mix together ground cinnamon and granulated sugar for the cinnamon-sugar mixture.

In a large mixing bowl, cream softened unsalted butter and granulated sugar until light and fluffy, about 2-3 minutes.

Add the eggs one at a time, mixing well after each addition, then stir in pure vanilla extract.

In a separate bowl, whisk together all-purpose flour, baking powder, and optional salt. Gradually fold this into the creamed mixture, alternating with milk and sour cream.

In your greased bundt pan, spoon in one-third of the batter, sprinkle with cinnamon-sugar, and repeat, swirling lightly.

Bake for 50-60 minutes. Check for doneness with a toothpick; it should come out clean or with a few moist crumbs.

Allow the cake to cool in the pan for about 10 minutes. Then invert onto a wire rack to cool completely.

To make the glaze, whisk together powdered sugar and cream/milk until smooth. Drizzle over the cooled cake.