This recipe is used in our Blueberry and Coconut Cake.
Preheat oven to 325 degrees. Coat two 9-by-2-inch round cake pans with cooking spray; line with parchment paper. Set aside.
Sift flour, 1 3/4 cups superfine sugar, baking soda, and 1/2 teaspoon salt into the bowl of an electric mixer fitted with the paddle attachment. Whisk together 3/4 cup water, the vegetable oil, egg yolks, and vanilla in another bowl. Add yolk mixture to flour mixture; mix on medium-high speed until smooth, about 2 minutes. Transfer to a large bowl; set aside.
Put egg whites and a pinch of salt into the clean bowl of a mixer fitted with whisk attachment; beat on medium speed until foamy. Raise speed to medium-high; beat until soft peaks form. Gradually add remaining 1/2 cup superfine sugar; beat until stiff, glossy peaks form.
Fold one-quarter of the egg-white mixture into the batter with a rubber spatula; fold in remaining egg-white mixture in 2 batches. Fill prepared pans 1/3 full with butter, and lightly stud batter with half of the blueberries.
Divide remaining batter between the two pans and lightly stud batter again with more blueberries. Bake until cakes are golden and spring back when pressed, 30 to 40 minutes. Invert cakes onto wire racks to cool; remove parchment.