In a saucepan, place the collard green ribbons with a touch of salt and the vegetable stock or water. Cover and cook about 8-10 minutes over medium heat, stirring frequently to make sure they don't stick to the bottom. If they do, add some more stock or water.
Add the coriander seed powder, cumin powder. dry chilies broken into pieces, and turmeric. Stir well to mix and cook another couple of minutes.
Add the cooked dal and, if it's too thick, thin it out with water. Add the ground black pepper. Bring to a boil and let the dal cook with the spices and the collards for another 10 minutes.
In a small pan, heat the oil for tempering. Add mustard seeds and, when they sputter, add the garlic slivers. Saute until they start to color.
Pour the oil with mustard seeds and garlic into the dal and mix well. Add salt if needed, squeeze in the lemon juice, and serve hot.
Serve this dal hot with rice or rotis, and a vegetable side (sabzi) like this gobi masala.