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
1/4 teaspoon baking soda
1/2 teaspoon baking powder
1/4 teaspoon salt
Source: http://www.tastebook.com/recipes/2743407-Everyday-Chocolate-Cake