Clip the tops off your beets and scrub them well to remove any dirt on the skins. Place the beets on a large piece of foil and pour the oil over them.
Fold the foil into a pocket or tent, completely closing up the foil around the beets.
Once you have it closed, place the entire package on a cookie sheet or in a baking dish. Bake at 350 F. until soft and easily pierced with a fork. (Time will depend on size of beets) Allow them to cool enough that you can handle them without burning yourself.
Peel the skins off. Chop into small pieces.
Spread those pieces in a baking dish and pour the citrus juices over them.
Make sure that the beats are in a single layer so all pieces are laying in the juice to marinate. Cover with plastic wrap and place in the fridge overnight (or at least for 2 hours minimum).
Please note that the nutrition data given here is a ballpark figure. Exact data is not possible.