Heat the oil in a heavy frying pan over moderate to high heat. Add the mustard seeds to the hot oil until they pop. Raj cooks the green pepper at this point until soft, 2-3 minutes. Add the cabbage and stir, mixing in the spices until well blended. Cook to preferred doneness (5-20 minutes), stirring occasionally to keep the cabbage from harm.
Fully cooked cabbage should be half in volume from the original. Remove from heat when done and mix in lemon juice.