Heat oil in wok or skillet over high heat. Add the mustard seeds and asafetida, if using and wait for the mustard seeds to crackle.
Reduce heat to medium and stir in the tomato onion masala sauce. Mix into the mustard seeds. Add the magic masala or garam masala.
Add cabbage to the sauce along with ½ cup water and mix it well.
Bring to a boil, then cover the pan and cook about 10 minutes until the cabbage is very soft. Stir occasionally while cooking to make sure the cabbage cooks evenly.
Once the cabbage is soft, add salt and mix it in. Serve the cabbage masala hot.
Notes
*You can also find Maggi masala magic powder at most Indian grocery stores or online.