Moist pound cake
Generously grease the bundt cake pan with cold butter. It will warm up as you move it around the pan with your fingers. Be sure to get the butter into every corner of the pan. Put the buttered pan in the refrigerator while you make the batter. (Refrigerating the buttered pan will ensure that the butter coating firms up so it doesn't move when the thick batter is poured into the pan).
Preheat the oven to 325 degrees.
In a large bowl, or stand mixer fitted with the paddle attachment, mix the butter, sugar and orange zest until light and fluffy, around 3-5 minutes.
Add the eggs one at a time. Blend until incorporated. The batter may look a little curdled. This is normal. Use a spatula to scrape the bottom of the bowl to ensure that nothing gets stuck there.
Add the vanilla and half of the buttermilk. Blend until incorporated.
Mix all of the dry ingredients together with a whisk (flour, baking powder, baking soda and salt). Add half of the dry ingredients to the batter. Blend on low speed until mostly incorporated.
Add the other half of the buttermilk. Blend until mostly incorporated.
Add the remainder of the dry ingredients and blend until mostly incorporated. Remove the bowl from the stand mixer. Finish mixing the batter by hand with a spatula. Be careful not to overmix the batter.
Remove the cake pan from the refrigerator. If you're using an intricate bundt cake pan, you will want to lightly flour the pan for extra insurance. Tap the extra flour out before pouring the batter into the pan. For best results, be sure to not to fill the cake pan more than 3/4 full. To ensure that the batter settles into every crevice of the bundt cake pan, gently tap the batter-filled bundt cake pan a few times on a hard surface. (I do NOT recommended doing this on your countertop or hardwood/vinyl/tile floor, as they can be damaged). I usually put a couple pieces of cardboard down on the floor before gently tapping.
Bake the cake at 325 degrees on the middle oven rack for 60 minutes, or until a toothpick inserted into the centre of the cake comes out clean.
Allow the cake to cool for 10 to 15 minutes before inverting the cake onto a serving plate. Shake the pan from side to side to determine if it has released from the sides of the pan. If not, check again in five minutes.