Here's another recipe that I've had for awhile, just haven't posted it until now.
This may be halfed, it makes a lot.
Microwave Cake (Gluten-free, Dairy-free, Corn-free, Egg-free)
1/2 cup gluten-free flour (rice)
1/4 teaspoon guar gum
1/4 cup sugar
1/8 teaspoon baking soda
1/8 teaspoon cream of tartar
1 tablespoon cocoa powder (if you want a vanilla cake, omit cocoa)
1/4 teaspoon vanilla
1/4 cup + 1 tablespoon water (if not dairy-free, you may use milk)
1 teaspoon oil
Mix all ingredients well. Spray a microwave-safe bowl or cup with cooking spray, and pour the batter into the cup.
Microwave at full power for 1 minute. Depending on the strength of your microwave and shape of you cup, you may need to cook the cake longer in 15 second increments until done. As long as you don't overcook it, it won't turn rubbery. The cake will puff up, so don't fill a very small container - it needs some room to rise.
~ Hanunyah