As you know, when I make a recipe that calls for buttermilk, I usually end up using lactose-free milk with a splash of lemon juice or vinegar. And according to Cook’s Illustrated, it’s not necessary to let the mixture curdle; you get the correct pH right away to carry on with the recipe. The downfall of that method, of course, is that you don’t get the same taste as buttermilk, which can be noticeable in a recipe where buttermilk is the star. That’s why I sat on this Bon Appétit recipe for a while, until I read that some people are replacing buttermilk with plain yogurt. The consistency isn’t quite the same, but the taste is tangier, closer to what was intended. So that’s what I tried here. I baked the cake less than the recipe calls for, to compensate, and the Engineer and I really liked the results (though the Texas blackberries I had were huge, and smaller ones would have been better here). Next time, though, I’ll try replacing the buttermilk with half lactose-free plain yogurt and half lactose-free milk.
¾ cup (1 ½ sticks) unsalted margarine, plus more for pan and parchment
2 1/3 cups (9.3 oz.) cake flour (sifted, then measured), plus more for pan
2 ½ cups (10 oz.) fresh blackberries
¼ cup plus 1 1/3 cups sugar
1 ½ tsp. baking powder
¾ tsp. salt
½ tsp. baking soda
3 large eggs, room temperature
2 tsp. vanilla extract
1 ½ tsp. finely grated orange zest
1 cup well-shaken buttermilk substitute (see above)
powdered sugar (for dusting)
Position a rack in middle of oven and preheat to 350 °F. Grease a 9” or 10” springform pan; line bottom with a round of parchment paper. Grease parchment. Dust with flour; tap out excess. Arrange berries in a single layer in bottom of pan; sprinkle evenly with ¼ cup sugar.
Sift flour, baking powder, salt, and baking soda into a medium bowl; set aside. Using an electric mixer, beat margarine and remaining 1 1/3 cups sugar in a large bowl at medium-high speed, occasionally scraping down sides of bowl, until pale and fluffy, about 2 minutes. Add eggs, one at a time, beating well after each addition. Beat in vanilla and zest. Reduce speed to low; beat in flour mixture in 3 additions, alternating with buttermilk substitute in 2 additions, beginning and ending with flour mixture and beating just until incorporated. Pour batter over berries in pan; smooth top.
Bake until cake is golden brown and bounces back when pressed gently with fingertip, about 1 hour 25 minutes for a 9" pan and about 1 hour for a 10" pan (I had a 9” pan with 1 cup of plain yogurt instead of the buttermilk, and 50 minutes was plenty). Let cool in pan set on a wire rack for 15 minutes, then run a thin, sharp knife around the edge of the pan to loosen. Remove pan sides. Invert cake onto rack and remove pan bottom; peel off parchment. Let cool completely. Dust top generously with powdered sugar.