Place the collard greens in boiling hot water. Let the collards cook eight minutes, then place them in a strainer to drain out all the water. Rinse the collard greens in cool, running water. Set aside.
Heat oil in a pan over medium heat and add asafetida. Saute for 30 seconds.
Add onions and garlic to the pan. Add ½ teaspoon salt and saute until the onions are very soft. Stir in the pureed tomato.
Add the spices to the pan: turmeric, Kashmiri chilli powder (or paprika), ground ginger and ground fennel.
Mix the spices into the garlic, tomato and onions in pan and continue to saute for five more minutes.
Add a cup of hot water to the pan and let it come to a boil. Stir in the blanched, drained collard greens and mix them in. Bring the collards to a boil, then turn heat to a simmer and let the collard greens cook, covered, for 20-30 minutes or until they are quite tender but have a good bite. You can tweak this to your preference--let the collards cook longer for more tender greens.
Stir in the garam masala and mix it in. You can add ½ to 1 cup more hot water at this point if most of the water has evaporated.
Continue to cook the collards for another five minutes. Add salt to taste. Turn off heat and serve hot.