Preheat the oven to 325℉ (160℃), then grease a 9x5-inch (1.25 pound) loaf pan for a wider loaf or a 8.5x4.5-inch loaf pan for taller loaf. Line the pan with overhanging parchment paper.
In a small bowl, whisk together the sifted flour, baking powder, and salt. Set aside.
250 grams cake flour, 1 teaspoon baking powder, ½ teaspoon fine sea salt
In the bowl of a stand mixer, fitted with paddle attachment on medium-high speed, cream together the softened butter and lemon sugar until light yellow and fluffy. This will take 3-4 minutes and I recommend scraping the bottom and sides of the bowl with a spatula a couple of times during. I use the number 6 speed on my stand mixer.
Mix in each egg one at a time. Scraping the bowl in between eggs to make sure everything is blending evenly. The mixture should be yellow and fluffy.
150 grams whole eggs
Next, mix in one third of the flour mixture completely. Stir the vanilla into the buttermilk and mix in half of the buttermilk until combined. Mixing well between each, scraping the bowl as needed.
160 grams buttermilk
Blend in the second third of flour, followed by the second half of buttermilk. It may look slightly curdled, but will smooth out in the final step.
Finally, mix in the remaining third of the flour mixture until just combined to make a thick smooth cake batter. Scrape that bowl again as needed. Don't leave anything stuck to the bottom.
Spoon the cake batter into the prepared cake pan. Take a small spatula and level the cake batter while knocking out any air gaps.
**For a picture-perfect crack down the middle, dip a sharp knife in melted butter and draw a line in the middle of the cake. Only cut about 1/8-inch deep. This is optional and only for aesthetics.
Place the pan on the middle oven rack and bake for 75-85 minutes. Tent with a piece of aluminum foil at the 50 minute mark to prevent over-browning.To check for doneness, insert a toothpick into the middle. If it comes out with just a few moist crumbs and no wet batter, the cake is done.
Place the pan on a wire rack to cool completely. To remove, pull up on the overhanging pieces of parchment paper and lift the cake from the pan.
Notes
Ingredients Used & Substitutions:
Flour: Swans Down Cake Flour 8% protein
Swap evenly for Gold Medal all Purpose Flour 10.5-11% protein
In France, use Farine T45 with 8.5% protein
Butter: President Unsalted Butter 82% butterfat (European style cultured butter)
Buttermilk: Swap for Greek yogurt or sour cream. This will result in a slightly denser, but still just as tasty, final texture.
Oven: This recipe was written for a conventional oven (top and bottom heat). For convection fan ovens, reduce the temperature by 25 degrees and begin checking for doneness 75% of the way through baking.
Weigh your flour: The measurement I use: 1 cup of flour equals 125 grams. This amount can change based on a different baker’s recipe or using a conversion tool. The weight listed in the recipe is how it was tested and should be used for accuracy.Different brands of flour are made with soft or hard wheat and have varying levels of protein, ranging from low to high. This can change the final result of a baked good, giving different outcomes on the same recipe. See My Baking Ingredientsfor additional details. When choosing a flour, look at the protein level on the back of the bag and consult the recommended amount for the recipe.