I made some changes & got a dark coloured cake .
Ingredients : 1/2 cup gehun ka atta,1/2 cup ragi flour,2 tbsp unsalted butter,1/2 cup powdered or grated jaggery,baking powder 3/4 tsp,1/2 cup sugar,1/2 tsp vanilla essence,1tbsp vinegar,milk for making the batter get a drop down consistency,4-5 slices of fresh pineapples.
Method :Grease the microwaveable vessel with oil or ghee & keep aside.
Take a pan & melt the butter.Add the jaggery to the melted butter & mix.The moment ,the mixture starts bubbling,put off the gas.Cool this mixture a bit & pour it into the greased vessel.
On top of this mixture,line the vessel with pineapple slices.
Sieve the atta,ragi flour & baking powder together.Add sugar & salt.Mix nicely.
In another vessel ,mix vanilla essence,vinegar& the remaining pineapple slices which have been chopped finely.Add this mix to the ragi atta flour mix.Add milk to get a drop down batter consistency.
Now pour this batter into the microwaveable vessel.Microwave for 8 minutes.After 5-10 minutes test with a toothpik.If the toothpik comes out clean,cake is done.Let it cool out side the microwave for 15-20 minutes.Now ,turn it upside down on to a plate.After it has cooled off ,cut into desired shapes.If it is cut while it is still warm ,it might not cut properly.