everyday chocolate cake

INGREDIENTS

• 1/2 cup (1 stick or 4 ounces) unsalted butter, softened
• 1 cup (6 7/8 ounces) firmly packed light brown sugar
• 1/2 cup (4 ounces) granulated sugar
• 1 large egg, at room temperature
• 1 cup buttermilk
• 1 teaspoon vanilla extract
• 1 1/2 cups (6 3/4 ounces) all-purpose flour
• 3/4 cup (2 5/8 ounces) Dutch cocoa powder (see above for a natural cocoa adjustment)
• 1/4 teaspoon baking soda
• 1/2 teaspoon baking powder
• 1/4 teaspoon salt