Grease round micro-proof baking dish, 7 1/4 x 2 1/4 inch 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) for 40 to 50 seconds. In a 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 it stand 5 minutes, invert onto serving plate. Peel off plastic wrap; cool, frost.