Soak the chana dal in water for 1 hour. Drain, rinse and set aside.
For Pressure Cooker or Insta Pot Method: Warm oil/ghee to the pot. Add the cumin seeds, bay leaf, black cardamom, chopped onions. Saute for 3-4 minutes until the onions start to soften. add the garlic, ginger, salt and tomatoes, stir and cook for 2 minutes. Now add the turmeric, coriander, dal and lauki, mix well. Add up to ¼ cup water.
Secure the lid, close the pressure valve and cook for 10 minutes at high pressure. Or in case of pressure cooker once the valve whistles lower the heat and cook for 10 minutes. Naturally release pressure. Taste and adjust the seasoning. Garnish with cilantro and serve with roti or steamed rice.
For conventional method cook in a large sauce pan with fitted lid for 25-30 minutes until the dal is tender and lauki is fully cooked. You may need little extra water in case the dal dries out. I have always cooked this stew in a pressure cooker, so can't be 100% accurate about the conventional method.