Preheat the oven to 350 F (177 C). Grease a 10-inch (12 cup capacity bundt pan).
In a medium sized bowl whisk the all purpose flour, baking powder and salt together until well combined.
Pour the sugar into a different medium sized bowl. Zest all the lemons right into the sugar. This is the best way to extract all oils from the lemon and get the best lemon flavor.
In the bowl of a stand mixer with whisk attachment, beat the butter and oil on medium speed until smooth and well combined.
With the mixer on low, slowly pour the lemon zest sugar into the butter and oil mixture. Once all the sugar has been added, increase the speed to medium for about 3 minutes or until the butter and sugar are fluffy and light in color.
On the lowest speed, mix in each egg one at a time. Wait for each egg to be fully incorporated before adding the next. This takes about 20 seconds per egg. Once all the eggs are mixed in, mix in the sour cream and fresh lemon juice. The mixture may look grainy or even a little curdled. Don’t worry, this is exactly how it should look at this stage.
By hand or on the lowest setting of your mixer, mix in the dry ingredients to the wet, alternating with the milk. This will be done in three rounds- dry, milk, dry, milk, dry, milk. If you are familiar with lemon pound cake, this cake batter will look very similar.
Pour the easy lemonade cake batter into the prepared bundt cake pan. Bake the lemonade cake for about 40 - 50 minutes. The cake is finished when the edges of the cake are pulling slightly away from the pan, the top is golden brown and bounces back when gently pressed.
Remove the bundt cake from the oven to cool on a cooling rack for about 10 -15 minutes. After this time, place a serving plate or even another cooling rack on top of the bundt pan. Invert the pan so the top of the bundt cake is now on the bottom (on the serving plate or second cooling rack). Gently tap all around the pan to help loosen any pieces of cake that may be stuck. Gently lift up the pan. Allow the cake to cool to room temperature before applying the fresh lemon glaze. Make the fresh lemon glaze by whisking the lemon juice into the powdered sugar. Pour the glaze over the cooled cake. Allow another 30 minutes for the glaze to set. Slice and enjoy!