Preheat the oven to 350°F conventional or 325°F convection(with fan). Zest the lemon into your sugar. Rub it gently between your fingers to start releasing the oils in the skin. This will draw out more flavor than simply adding it to the batter!
Butter and flour your pan. This recipe makes either one 12 cup Bundt pan or two large loaf pans.
A thorough but thin coating is essential to a perfect bundt cake that doesn’t stick. Spray non-stick cooking spray or brush butter the inside of the bundt pan. Add a little flour to the pan. Tap the outside of the pan as you rotate it. Now reverse the direction of the rotation and repeat. This second rotation is only necessary if you are using an ornate bundt pan. Tap out the excess on a towel or parchment on a countertop. Now drop the pan upside down on the parchment or towel. This will release all the excess flour and you should have a beautiful, light dusting of flour inside your pan. Well done!
In a large mixing bowl, whisk together flour, baking powder, and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment or in a large bowl with an electric hand mixer, beat butter, shortening and sugar just until the mixture comes together and it is no longer lumpy or clumpy. It will look like a paste.
Add eggs to the mixer bowl, one at a time, beating after each one until just incorporated.
Add flour mixture in three additions alternating with first the lemon juice then the milk, starting and ending with flour. Don’t worry if your batter appears curdled after adding the milk. This is less likely to happen if you have all ingredients at room temperature. Mix after each addition only until just blended.
Working quickly, pour batter into prepared pan(s) until they are a little more than ¾ full. If you dilly-dally they will fall, and then they will look sad, and we don’t tolerate sad.
Bake cakes in preheated oven until tester comes out with only a few crumbs attached. Approximately 55 minutes for a large Bundt pan and 35 minutes for small pans. I personally would start testing my large Bundt cake after 35 minutes or when the center no longer looks wet because I abhor dry cakes. It is done when a metal skewer or toothpick comes out with a few clinging crumbs. Convection will help the cakes bake faster and more evenly but it isn’t necessary and the resulting lemon bundt cake will be moist, dense and perfect.
Allow to cool 30 minutes in the pan then turn out on a wire rack to cool completely. If the cake will not release easily, don’t panic, try running an offset spatula around the center tube to release the cake, then try turning out again. If it will not release easily, wait until the cake cools completely. Try again. If it will not release when completely cool, you are allowed to panic just a little. Try gently loosening the edges and turning over to test.
By this time you should be able to tell where the cake is sticking, if you can’t, then it is probably the top of the mold (the top of the cake when inverted). You might have to do some minor surgery. You can cover most blemishes with glaze.