M: 240 grams (2 cups) cake flour, plus more for the pans 2 teaspoons baking powder 1/2 teaspoon baking soda 1/2 teaspoon table salt 1 cup buttermilk, room temperature 141 grams (10 tablespoons) salted butter, melted and slightly cooled 2 large eggs, plus 2 large yolks, room temperature 2 tablespoons grapeseed or other neutral oil 1 tablespoon vanilla extract 268 grams (1 ¼ cups) white sugar
Step 1 Heat the oven to 350°F with a rack in the middle position. Mist two 8- or 9-inch round cake pans with cooking spray. Line the bottoms with rounds of kitchen parchment, then mist the parchment. Dust the pans with flour, then knock out the excess. Step 2 In a large bowl, whisk together the flour, baking powder, baking soda and salt. In a blender, combine the buttermilk, butter, whole eggs and egg yolks, oil, vanilla and sugar. Blend on high just until combined, about 15 seconds, scraping the jar about halfway through to make sure the sugar has not clumped on the sides; do not overblend. Pour the wet ingredients into the dry ingredients, then whisk just until evenly moistened. Divide the batter evenly among the prepared pans, then rap each pan 2 or 3 times on the counter to remove any air bubbles. Step 3 Place the pans in the oven, evenly spaced on the rack. Bake until golden brown and a toothpick inserted in the centers comes out clean, 22 to 25 minutes. Cool in the pans on a wire rack for 15 minutes. Run a paring knife around the edge of each cake to loosen. Invert the onto the rack, lift off the pan and peel off the parchment. Cool completely, about 1 hour.
That was a recipe I want to do, but I don't have flour that is specifically cake flour. And we can't remember the substitute for buttermilk. So I could use a little bit of help with these.
G: Yep. Both substitutions are easy here, and this particular cake is forgiving enough that I wouldn't hesitate to use them.
For the 240 g / 2 cups cake flour, use all-purpose flour plus cornstarch:
That approximates cake flour by lowering the overall protein content. Since your recipe gives the flour by weight, an even cleaner approach is roughly 210 g all-purpose flour + 30 g cornstarch = 240 g total.
For the 1 cup buttermilk, the standard quick substitute is:
1 tablespoon lemon juice or white vinegar + enough regular milk to make 1 cup.
Stir it and leave it alone for about 5–10 minutes. It'll thicken/curdle slightly. Then use the entire cup exactly where the recipe calls for buttermilk. Whole milk is best for this cake, but 2% will work perfectly reasonably.
One thing that's actually important here: don't just substitute ordinary milk without acid. Your recipe has ½ teaspoon baking soda, and the acidity of the buttermilk is part of what activates it. The lemon/vinegar milk substitution preserves that chemistry.
So if you've got all-purpose flour, cornstarch, milk, and either lemon juice or white vinegar, you don't need to buy either cake flour or buttermilk.