In a bowl soak 1 tablespoon tamarind and ¼ cup warm or hot water for 20 to 30 minutes.
Then later squeeze the soaked tamarind pulp in the water. Keep this tamarind pulp aside.
Rinse ½ cup tuvar dal (pigeon pea lentils) a couple of times in water. Take the lentils in a medium sized bowl.
Add ¼ teaspoon turmeric powder and salt as per taste. Add 1 cup water.
Place the bowl in a pressure cooker. In the pressure cooker add 1.5 cups water. Here I have used pot in pot method of cooking both rice and dal. You can also just cook dal alone in the pressure cooker. If cooking dal directly in the pressure cooker, then add 2 to 2.5 cups water. cover the bowl with a lid.
Cover and pressure cook dal for 7 to 8 whistles or 10 to 11 minutes on medium flame.
When the pressure settles down on its own, open the lid and check the dal. The dal should be completely cooked and mushy. Mash dal with a spoon or wired whisk. Cover and keep aside.
Rinse, peel and chop 250 grams pumpkin in large pieces. Add the chopped pumpkin in a pan. You will need 2 cups chopped pumpkin. If you want you can keep the peels on the pumpkin.
Add 1 pinch turmeric powder and 1 cup water.
Cover the pan and cook pumpkin on a low to medium flame till its tender. in between do check when the pumpkin is cooking.
The pumpkin cubes should be cooked and tender, but do not overcook them or make them mushy.
making pumpkin sambar
When the pumpkin cubes are cooked, add the tamarind pulp.
Add 1 to 1.5 tablespoon sambar powder. Mix very well. then add the mashed dal. mix well.
Add ½ cup water or as required. For a thicker sambar, add less water.
Stir and mix again.
Simmer the sambar on low to medium flame for 6 to 7 minutes. The raw aroma of tamarind should go away. Switch off the flame after simmering for 6 to 7 minutes. Then cover the pan and keep aside.
making tempering for pumpkin sambar
Heat 2 tablespoons sesame oil (gingelly oil) in small pan or tadka pan.
Add 1 teaspoon mustard seeds and let them crackle.
When the mustard seeds crackle, then add 10 to 12 curry leaves and 1 to 2 dry red chilies (broken and seeds removed).
Immediately add 1 pinch of asafoetida (hing).
Mix well and fry till the curry leaves become crisp and the red chilies change color. Do not burn the red chilies.
Switch off the flame and immediately add the tempering mixture in the sambar.
Cover and let the flavors infuse for 4 to 5 minutes.
Then serve poosanikai sambar with steamed rice or with idli or dosa of your choice like