Ingredients
Vegetable-oil cooking spray
1 cup warm water
1/2 cup unsweetened natural cocoa powder
1 1/2 cups all-purpose flour
1 cup granulated sugar
3/4 teaspoon baking soda
1/2 teaspoon salt
1/2 cup sunflower oil
1 tablespoon pure vanilla extract
2 teaspoons distilled white vinegar
2 ounces dark chocolate (preferably at least 70 percent cacao), finely chopped
1/2 cup confectioners’ sugar, sifted
2 tablespoons water
Preparation
For the cake: Preheat oven to 375 degrees. Coat an 8-inch round cake pan with spray.
Whisk water and cocoa in a small bowl until smooth. Combine flour, sugar, baking soda, and salt in a large bowl, and make a well in center. Add cocoa mixture, oil, and vanilla. Whisk until smooth. Whisk in vinegar. Pour into pan.
Bake until a toothpick inserted into center comes out clean, 30 to 35 minutes. Let cool on a wire rack for 20 minutes. Run a knife around edge of cake, invert it onto rack, and turn cake right side up. Let cool completely. Transfer cake to a serving plate or a cake stand.
For the glaze: Melt chocolate in a heatproof bowl set over simmering water, stirring until smooth. Let cool slightly.
Whisk together sugar and water until smooth. Add melted chocolate in a slow, steady stream, whisking until thickened, about 1 minute. Immediately pour glaze onto center of cooled cake. Using an offset spatula, gently spread glaze over top and sides.
