If using fresh bamboo shoots, peel them and slice them thinly. Boil the bamboo shoots in water for about 10 minutes to remove any bitterness, then drain and set aside.
In a large pot, heat the vegetable oil or palm oil over medium heat.
Add the finely chopped onion and sauté until translucent, about 5 minutes.
Stir in the minced garlic and ginger, and cook for another minute until fragrant.
Add the chopped tomatoes and green bell pepper to the pot.
Stir in the ground turmeric, ground cumin, and ground coriander.
Cook for about 5-7 minutes, until the tomatoes have softened and the mixture is well combined.
Add the boiled bamboo shoots to the pot.
Pour in the vegetable broth or water, stirring to combine.
Season with salt and black pepper to taste.
Bring the mixture to a boil, then reduce the heat to low.
Cover the pot and let it simmer for about 20-30 minutes, or until the bamboo shoots are tender and have absorbed the flavors of the sauce.
Transfer the nswala to a serving dish.
Garnish with fresh cilantro or parsley if desired.
Enjoy your meal!