Preheat your oven to 350°F (175°C) and generously grease a 10- or 12-cup bundt pan.

In a small bowl, mix the brown sugar and cinnamon together and set aside.

In a large bowl, cream together the softened butter and granulated sugar until light and fluffy, about 3–5 minutes.

Beat in the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.

Add the dry ingredients to the wet batter in three parts, alternating with the sour cream. Mix just until combined.

Spoon half the batter into the prepared bundt pan. Sprinkle the cinnamon-sugar mixture evenly over the batter. Add the remaining batter on top and use a knife to gently swirl the layers.

Bake for 50–60 minutes, or until a toothpick inserted into the center comes out clean.

Let the cake cool in the pan for 10–15 minutes, then carefully invert onto a wire rack to cool completely. If desired, whisk together the glaze ingredients and drizzle over the cooled cake.