I add lemon juice to my Dhall.
I often do potatoes with it - precook the potatoes for a few minutes less than I would cook them to serve as straight potatoes, then add them to a oil + spice mix - the spice mix is turmeric, freshly ground coriander & cumin, red chili flakes and mustard seeds. pan fry for about 10 minutes.
The other side dish is mushrooms cooked in sesame oil, flavoured with lemon juice, one chopped red chili and bay leaves. I don't know why it works but it is especially good at freshening up dhall which has been in the fridge for a couple of days (served as a side, not mixed in with the dhall).