Preheat your oven to 180°C (350°F) and lightly grease a bundt cake tin with butter and dust it with flour to prevent sticking.

In a small bowl, mix the cinnamon and brown sugar for the cinnamon swirl. Set it aside.

In a large mixing bowl, cream the softened butter and caster sugar together until light and fluffy.

Add the eggs one at a time, with a teaspoon of measured flour to prevent curdling, beating well after each addition.

Sift the remaining self-raising flour into the mixture and fold it in until just combined.

Mix in the sunflower oil and whole milk until you have a smooth batter.

Pour ⅓ of the cake batter into the prepared bundt cake tin.

In a separate bowl, add ½ of the remaining cake batter to the cinnamon swirl mixture and evenly pour over the batter in the cake tin.

Add the remaining cake batter over the cinnamon swirl layer.

Use a knife or a skewer to create a marble effect by gently swirling it through the batter.

Bake in the preheated oven for approximately 40-45 minutes, or until a toothpick or skewer inserted into the center comes out clean.

Once done, remove the cake from the oven and allow it to cool in the tin for about 10-15 minutes.

Gently loosen the edges with a knife and then turn the cake out onto a wire rack to cool completely.

For the glaze, combine the glaze ingredients and add a small amount of water at a time until at correct consistency.

Once the cake has cooled, you can dust it with powdered sugar or drizzle with a simple glaze if desired.