Preheat the oven to 180°C (350°F) for conventional heat or 170°C (340°F) for fan-assisted / convection.

Generously grease the bundt pan with butter and dust with flour or breadcrumbs.

Sift the flour and baking powder together and set aside.

Place the butter, powdered sugar, and oil in a large mixing bowl.

Beat on high speed until the mixture becomes pale, light, and fluffy – about 3 minutes.

Add the eggs one at a time, along with 1 tablespoon of the sifted flour per egg. Mix briefly on low speed, just until combined.

Add about half of the remaining flour and mix briefly.

Pour in the milk and mix shortly.

Add the rest of the flour and mix only until the batter comes together. Do not overmix.

Transfer about ⅓ of the batter to a separate bowl.

Add the cinnamon and brown sugar and mix thoroughly until well combined.

Spoon about half of the plain batter into the bottom of the bundt pan.

Add dollops of the cinnamon batter on top.

Cover with the remaining plain batter and smooth the surface. Use a knife or skewer to gently swirl the batter for a marbled effect.

Place the pan in the preheated oven and bake for about 50 minutes, or until a toothpick inserted into the cake comes out clean.

Remove the cake from the oven and let it cool in the pan on a wire rack for 5–10 minutes. Carefully loosen the edges, turn the cake out onto a plate, and allow it to cool completely.

In a small bowl, combine the powdered sugar and cinnamon. Add the maple syrup and 2 tablespoons of milk, then mix well. If the glaze is too thick, add a little more milk until smooth and pourable.

Drizzle or spread the glaze over the cooled bundt cake.