Peel the green plantains and cut them into 1/2-inch (1.25 cm) rounds.
If desired, you can blanch the plantain slices in boiling water for about 5 minutes to reduce bitterness. Drain and set aside.
Heat the vegetable oil in a large pot or skillet over medium heat.
Add the chopped onion and cook until translucent.
Stir in the minced garlic and cook for another minute.
Add the diced tomato and bell pepper. Cook for about 5 minutes, until the vegetables are softened.
Stir in the ground cumin, paprika, turmeric, salt, and black pepper.
Add the plantain slices and mix well to coat with the spices.
Pour in the vegetable broth or water and coconut milk (if using). Bring to a simmer.
Cover and cook for about 20-25 minutes, or until the plantains are tender and have absorbed the flavors. Stir occasionally.
Garnish with chopped fresh cilantro.
Enjoy your meal!