Wash the moong dal well. Drain and soak it in warm water for 15-20 minutes.
Meanwhile, get the rest of the ingredients ready.
Using a good peeler, peel only the sharp ridge portion of the gourd. Do not peel the entire green skin. That can be left intact.
Slice the gourd vertically and cut each half into a small dice.
Bring 1 cup of water to boil in a medium saucepan, along with the ginger and turmeric.
Drain the soaked moong dal and add it to the water in the pan along with the chopped ridge gourd.
Season with a pinch of salt, and allow this to cook for 8-10 minutes until the dal is soft and the vegetable is also cooked but not mushy.
While the dal is cooking, prepare the tempering.
Heat ghee in a small pan. Sprinkle asafoetida and stir quickly, adding the rest of the ingredients - cumin, cinnamon, green chillies and onions. Fry on a high flame for 4-5 minutes, until onion is slightly brown. Stir in the red chilli powder and garam masala if using. Transfer this tempering over the cooked dal + ridge gourd. Season with salt, around 1/2 teaspoon and simmer for 1-2 minutes, thinning with 2-3 tablespoons of water if required.
Garnish with fresh coriander and serve with steamed rice and a wedge of lemon.