Grease a bundt cake pan with cooking spray or a layer of shortening and then dust flour. Preheat your oven to 150 degrees Celsius or 350 degrees F.
Whisk the cake mix, confectioners sugar, and instant pudding mix in a large bowl using an electric hand mixer.
Add one egg at a time and keep beating using the electric mixer at high speed. Lower the speed to medium speed and add buttermilk and melted butter.
If you have a cup of fresh blueberries, toss them at this point, a lemon blueberry cake is also a perfect cake.
Continue mixing until a soft, smooth batter is formed. Using a rubber spatula, pour batter into the prepared pan.
Level out the top of the cake batter and put it in the preheated oven, preferably on the middle rack.
The average bake time for this cake is 45 minutes; check if it's ready by inserting a wooden skewer. When the skewer is clean, get the cake out of the oven and let it cool in the pan for about fifteen minutes. Remove from the pan to cool cake completely on a wire rack.