Preheat oven to 350 degrees F. Grease (shortening works better than butter in this case) and flour a standard 12-cup capacity bundt pan or spray with baking spray.: When you open the oven and feel that even warmth, you know the environment is right, and you will notice a subtle warmth on your face as the oven preheats. The reason for using shortening or a well greased pan is that it creates a thin fat layer between the batter and the metal, encouraging the cake to release cleanly, preventing tearing when you invert. A common mistake is not prepping the pan thoroughly, which leads to stuck edges and a broken presentation. If your pan is not well coated, use a pastry brush to get into crevices and dust with flour, tapping out the excess to ensure an even nonstick barrier.
In a bowl, sift together flour, cake flour, baking powder, and salt and set aside.: As you sift, the dry mixture will take on a light, airy appearance and you might hear a faint whisper of sifted powder falling back into the bowl. Sifting removes lumps and helps evenly distribute the baking powder and salt , which is critical for uniform rise and balanced seasoning. If you skip sifting, you risk pockets of leavening or dense spots, which can create uneven texture. Use a whisk to combine if you do not have a sifter, making sure the ingredients look homogeneous.
In a large mixing bowl or the bowl of a stand mixer fitted with the paddle attachment, beat butter and sugar on medium-high speed until light and fluffy, 2 to 3 minutes. Add eggs, one at a time, mixing well after each addition. Scrape down the sides of the bowl.: The sound changes from a soft thump to a higher pitch as air is incorporated, and the mixture lightens to a pale, billowy texture. This creaming step is essential because the trapped air helps the cake rise, and adding the eggs one at a time ensures the emulsion stays stable. If you add eggs too quickly, the batter can split, becoming curdled and less able to hold air. If you notice separation, reduce speed and scrape, then continue once it looks cohesive.
In a separate small bowl, whisk together Greek yogurt, milk, lemon juice, lemon zest, and vanilla until smooth and incorporated.: You will see the glossy texture of the Greek yogurt loosen with the milk , and the lemon oil released by the zest will scent the mixture. Combining these wet ingredients separately prevents overmixing later and ensures each addition introduces consistent moisture and flavor. A common error is adding cold dairy directly to the creamed batter which can curdle the mixture; using room temperature ingredients avoids that issue.
Add 1/3 of dry ingredients to mixing bowl and mix on low speed until almost incorporated. Add half of yogurt mixture and mix to combine. Repeat with another 1/3 of dry ingredients, remaining yogurt mixture, and ending with remaining dry ingredients, scraping down the sides of the bowl as needed, until just incorporated (do not overmix).: The batter will thicken and change from glossy to a more satiny texture, and you should watch for streaks to disappear rather than achieving a perfectly smooth pour. Alternating dry and wet ingredients prevents gluten overdevelopment, preserving tenderness. Overmixing at this stage creates a tougher crumb, so stop when you see the last streaks vanish. If you notice resistance and heavy batter, fold gently by hand once or twice to finish without overworking.
Pour batter into prepared baking pan and bake for 60 to 70 minutes or until a toothpick inserted in the thickest part of the cake comes out clean.: As the cake bakes you will smell a gentle lemon aroma rising, and the exterior will deepen to a warm golden brown. The oven's steady heat sets the crumb and encourages rise; opening the oven too often can cause the center to sink. A reliable check is inserting a toothpick into the deepest section; if it comes out with a few moist crumbs, the cake is done. If it jiggles in the middle, continue baking and check every 5 minutes to avoid drying out.
Remove from oven and let cool on a wire rack for 15 minutes, then invert onto a plate or serving platter and let cool upside-down for another 10 minutes. The cake should release itself, and you should be able to pull the pan off cleanly at this point. Let cool to room temperature before glazing.: The first cooling period allows the crumb to set, and the slight contraction helps the cake separate from the pan. When you invert, the warm steam escapes and the cake settles; this is why timing the inversion is crucial, too early and the cake can break, too late and it may stick. If the cake clings, tap the pan's edges gently or run a thin knife around the rim before trying again. Allowing the cake to reach room temperature before glazing prevents the glaze from melting into the crumb.
To make glaze, in a microwave-safe bowl or 4-cup capacity glass measuring cup, whisk together powdered sugar and lemon juice. Add lemon zest, butter, and salt and microwave for 15 to 20 seconds until butter is just melted. Stir until smooth. If you prefer a thinner glaze use it immediately, otherwise let it cool for 10 to 15 minutes or until slightly thickened. Drizzle over top of cooled bundt cake, then slice and serve. Cake is best served the day it is made, but will keep in an airtight container for up to 3 days.: The glaze will go from a snowy dry texture to a glossy ribbon as you whisk, releasing the citrus fragrance. Warming the butter just enough integrates it smoothly; overheating can separate the glaze. Use the glaze right away for a thin coat that settles into crevices, or let it thicken slightly for a more decorative drape. A common pitfall is adding too much juice which can make the glaze runny; if so, add a touch more powdered sugar to reach desired consistency.