In a mixing bowl, crumble the cake that you have using your fingers or two forks. In a microwaveable bowl, take the dark chocolate chopped into small pieces. Add two tbsp of butter to it. Then on a medium power, microwave for 30 to 40 seconds, stopping every 20 seconds to check and give a stir. Basically you will have to melt the chocolate without the chocolate seizing in the bowl. It might take a minute or so. It depends on the microwave power.
In case you do not have a microwave, then take a heavy bottomed pan and toss the ingredients in the pan. Over very low flame stir and melt. Ideally it should be done on a double boiler but we are not going to need tempered chocolate here.
Once the chocolate has melted, add it to the cake crumbs. Using a fork, mix thoroughly and then use your hands to knead the mix into a nice smooth dough. If you feel that it is not coming together, add more butter as required.
Once the dough comes together, shape them into small balls and keep aside.
In a bowl, take the beetroot powder and then take the balls one by and one and coat them with beetroot powder.
You can serve them immediately. In case you want to serve later, then it is best to store the cake pops in the refrigerator without the beetroot powder and dust with beetroot powder just before serving.