2 cups all-purpose flour
2/3 cup unsweetened cocoa powder
1 teaspoon baking soda
1/2 teaspoon cinnamon
1/4 teaspoon salt
1/4 teaspoon baking powder
3 large eggs
1 2/3 cups packed light brown sugar
2 teaspoons vanilla extract
1 cup mayonnaise
1 1/3 cups hot water
Frosting:
1 (8-ounce) package cream cheese, softened
1/2 cup butter, softened
2 teaspoons vanilla extract
1/2 cup unsweetened cocoa powder
4 1/2 to 5 cups powdered sugar
2 tablespoons heavy cream
Preheat oven to 350 degrees and spray a 9x13-inch pan with baking spray with flour. In a medium bowl, whisk together the flour, cocoa powder, baking soda, cinnamon, salt, and baking powder. Set aside. Using an electric mixer, beat eggs, brown sugar, and vanilla extract at medium-high speed for 3 minutes. With mixer on low, add mayonnaise and beat just until combined. Alternate between adding flour mixture and hot water, (adding flour in 3 additions and water in two and beating just until mixed in before adding next addition). Pour batter into prepared pan and bake for 30 to 35 minutes. Let cool before frosting. To make frosting, beat cream cheese, butter and vanilla with an electric mixer until creamy. Whisk together the cocoa powder and powdered sugar. Beat half the mixture into the butter mixture. Beat in the heavy cream and then the remaining powdered sugar mixture. If too thick, add a little more cream. Spread frosting on cake.