Preheat your oven to 350°F (180°C). Spray or grease and flour your 7½ inch bundt pan or 8 inch round cake pan thoroughly. I use a baking spray with flour for this — it gets into every nook and cranny.
Sift the Dry Ingredients: In a medium bowl, sift together the cake flour, salt, baking soda, and baking powder. Sifting aerates the flour and ensures the leaveners are evenly distributed.
Cream the Butter and Sugar (The Long Version): In a large bowl or the bowl of a stand mixer fitted with the paddle attachment, beat the softened butter and granulated sugar on medium speed for a full 8–10 minutes. I know it feels like forever, but this is where the texture magic happens. Scrape down the sides and bottom of the bowl halfway through. The mixture should be very light in color, fluffy, and look almost like a thick paste.
Add the Wet Ingredients: Add the lemon extract (or vanilla) and lemon zest to the butter mixture, then add the eggs one at a time, beating well after each addition until fully combined and smooth. If the mixture looks slightly curdled at this point, don't panic — it will come together when you add the flour.
Alternate Flour and Buttermilk: With the mixer on low speed, add the sifted flour mixture in three additions, alternating with the buttermilk in two additions, beginning and ending with the flour. Mix just until combined — about one minute total. Overmixing at this stage develops gluten and makes the cake tough.
Bake: Pour the batter into the prepared pan and spread it evenly. Place in the oven, then immediately reduce the temperature to 325°F (165°C). Bake for 40–45 minutes, or until a toothpick inserted in the center comes out clean or with just a few moist crumbs. The top should be golden brown and springs back when gently pressed.
Cool: Let the cake cool in the pan on a wire rack for 15 minutes. Then invert onto the rack and cool completely before dusting with powdered sugar. If you try to unmold too early, the cake may stick or break.