Preheat oven to 350ºF (180ºC).
Grease a 10 or 12-cup bundt cake pan (26cm) with 2 tablespoons shortening, covering every angle, nook and cranny. Dust with 2 tablespoons flour, shaking off excess. Reserve.
Beat 1 cup unsalted butter in a large bowl at medium or high speed, while adding 2 cups sugar gradually until the mixture is creamy, about 3 minutes. You can use a hand-held electric mixer or a stand mixer.
Add 4 eggs, one at a time, beating well each time to combine.
Add ½ teaspoon vanilla extract and 1 tablespoon lemon zest and mix.
Sift 2 ¼ cups all-purpose flour, 1 teaspoon baking powder and ¼ teaspoon salt (I have them measured and sift them directly into the batter) and add them in 3 parts to the egg mixture, alternating with ½ cup sour cream, ¼ cup milk and ¼ cup fresh lemon juice in 2 parts. So you add: ⅓ of the dry ingredients, then the sour cream and half the milk and mix, then ⅓ more of the flour, the rest of the milk and lemon juice, and the final ⅓ of the dry ingredients.
Mix lightly at low speed every time you add a dry or wet part; there's no need to beat thoroughly after each addition, except the last one. Mix well but don’t over beat. I highly recommend you run a rubber spatula at the end and make sure there are no dry spots before pouring the batter into the pan.
Pour mixture into the prepared bundt pan.
Bake for about 45 minutes, or until a tester comes out clean. This time is estimated according to my oven and pan, but it can take a little less or more for you. So start checking towards the 35-40 minute mark. Cover loosely with a piece of aluminum foil if the top of the cake browns too quickly and continue baking until completely done.
Let cool 20 minutes on a wire rack and carefully shake the pan to see if the cake loosens by itself. You can use a smooth-bladed knife and insert it between the cake and the edges of the pan and gently loosen the parts that might've stuck during baking. Again shake the pan carefully. You should feel that the edges and the bottom of the cake is loose.
Remove the cake by putting the wire rack or a plate on top of it and flipping it with both hands with a kitchen towel that allows you to grasp both the wire rack (or plate) and the edges of the cake pan at the same time. Remove the bundt pan and flip the cake with the wire rack so it's on top of it again but without the pan.
Let the cake cool completely on the wire rack before glazing.