There are two kinds of Sambar. A simple Kind, And this one where you use freshly ground spices.
Cook the toor dahl. See Recipes for Cooking Toor Dahl. Use this Link : https://versatilefoodie.com/category/indian-basic ~ Note: After cooking the Toor Dahl, let it sit for 30 minutes, or at least 15 minutes, so that the Toor Dahl can be mashed well.
Slice each bitter gourd lengthwise. Scoop out the seeds. Slice them into 1/4 inch thick pieces.
Place the bitter gourd pieces in a saucepan. Add water so that it is about 3 inches above the vegetable. Add 1 teaspoon salt and 1 teaspoon turmeric. Boil until the vegetable is well-cooked but firm. Do not overcook.
Drain the vegetable in a colander. Set aside.
Place a small frying pan on medium heat. Add 1 teaspoon oil.
When oil is hot, add whole red chilies, coriander seeds and channa dahl . Fry until channa dahl is golden brown. Do not fry too much.
Add the coconut pieces and stir fry for a minute more, or until the coconut pieces are slightly roasted. Set aside the frypan and let it cool.
Place the fried spices in a blender/grinder. Add half a cup of water. Grind the contents. If paste is too thick to grind, add 2 tablespoons of water at a time, as necessary, until it turns into a smooth paste. The paste should be like thick pancake batter, not too thick, not too thin.
Transfer the ground paste into a bowl. If the paste is too sticky in the blender, you can add 2 tablespoons of water and pour it out into the bowl. Set the Spicy Paste aside.
Place a large sauce pan on medium heat. Add 3 tbsp oil. When oil is heated add mustard seeds. When they crackle rapidly, add the drained bitter gourd pieces into the sauce pan.
Mash the cooked toor dahl well. If necessary, use a hand held mixer and pulse just once or twice until the toor dahl is mashed.
Add the mashed toor dahl to the saucepan. Mix well.
Add the blended spice paste into the sauce pan. Stir the ingredients gently without breaking the veggie pieces. Let it simmer for 2 more minutes.
Taste a little. Add more salt or tamarind, if necessary according to your taste.
Serve hot as a Gravy on a bed of Rice, Or as a Side Dish with any kind of Idlis, Dosas and Vadas.