Preheat your oven to 350°F (175°C) and grease a bundt pan with butter or non-stick spray.

In a small bowl, mix brown sugar and ground cinnamon for the filling.

Cream together softened butter and granulated sugar for 4-5 minutes until light and fluffy.

Add eggs one at a time and then blend in vanilla extract until smooth.

Whisk together all-purpose flour, baking powder, and salt in a separate bowl.

Gradually mix the dry ingredients and milk into the butter mixture, alternating between them.

Pour half of the batter into the prepared bundt pan, followed by the cinnamon mixture, and top with remaining batter.

Gently swirl through the layers of batter with a knife or skewer for a marbled effect.

Bake for 50-60 minutes until a toothpick comes out clean.

Cool the cake in the pan for 10-12 minutes before inverting it onto a wire rack.

Prepare the glaze by mixing powdered sugar with a little milk until smooth.

Drizzle the glaze over the cooled cake before serving.