For a chocolate cake, add 1/3 cup cocoa powder. For a vanilla cake, add another teaspoon of vanilla extract. Cook the cake in the microwave for 3-4 minutes on full power. The cake will bubble and puff in the microwave just as it would in the oven. Just as it starts to set (it'll still be jiggly), it's done.  Check to see if the cake is baked by sticking a toothpick straight down into the center. The toothpick should come out clean. If there is gooey cake residue on the toothpick, put the cake back in the microwave and cook it in 1 minute increments until done. Take care not to overcook. If you microwave the cake for too long, it will likely dry out. Served warm, this cake is super moist and totally irresistible. Top with frosting and decorate if you'd like.

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Write a summary of the previous text in Vietnamese:
Thêm hương vị cho bánh. Nướng bánh. Thưởng thức.