In a large bowl,Cream the butter with a whisk or a hand whiske till it turns pale.
Add the sugar and again whisk till the sugar crystals start to dissolve and it looks like a very light yellow paste.
In a separate bowl mix the flour,baking powder,cinnamon and salt and set aside.
Combine the buttermilk and the orange juice.
Add the juice mixture and the flour mixture to the creamed butter alternatively and combine.Add the vanilla extract and the orange zest.
Add the eggs one by one and mix.
Bake in a preheated oven at 180 degrees for 40-50 minutes till the skewer comes out clean.
Once cooked,take out of the oven and let it cool in the pan for 10 minutes.
Gently transfer to a wire rack and cool till at room temperature.
Sift the caster sugar.
Whisk the caster sugar,orange zest and orange juice till you get a thick glaze.
Once the cake has cooled pour over it.
I have used a bundt pan.You can use a normal pan too but keep an eye on the cooking time. I used freshly squeezed orange juice for this cake but you can use store bought orange juice also but adjust the sugar accordingly.