1/4 c. Hershey's cocoa 
2/3 c. hot water, divided 
3/4 c. plus 2 tbsp. all-purpose flour 
1 c. sugar 
1/2 tsp. baking soda 
1/4 tsp. baking powder 
1/4 tsp. salt 
1/4 c. plus 2 tbsp. vegetable oil 
1 egg 
2 tsp. vanilla extract 
Easy Cocoa Frosting

Grease round micro-proof baking dish, 7 1/4 x 2 1/4 inches or 8 x 1 1/2 inches; line bottom with plastic wrap. In small micro-proof bowl, combine cocoa and 1/3 cup water; microwave on high (full power) 40 to 50 seconds or until very hot and slightly thickened. In medium bowl, combine flour, sugar, baking soda, baking powder and salt. Add oil, remaining 1/3 cup hot water, egg, vanilla and chocolate mixture; beat until batter is smooth and well blended. Pour batter into prepared pan. Microwave on high 5 to 6 minutes without turning until cake begins to pull away from sides (some moist spots may remain but will disappear on standing). Let stand 5 minutes; invert onto serving plate. Peel off plastic wrap; cool. Frost. About 8 servings. *Time is for 600-700 watt microwave ovens.
 

Source: http://www.nancys-kitchen.com