Devils food mini bunt cake with cream cheese frosting

Devil's Food Cupcakes  "Martha Stewart's Cupcakes"

INGREDIENTS 3/4 cup unsweetened Dutch-process cocoa powder 3/4 cup hot water 3 cups all-purpose flour 1 teaspoon baking soda 1 teaspoon baking powder 1 1/4 teaspoons coarse salt 1 1/2 cups (3 sticks) unsalted butter 2 1/4 cups sugar 4 large eggs, room temperature 1 tablespoon plus 1 teaspoon pure vanilla extract 1 cup sour cream, room temperature Top with cream cheese frosting