Heat the coconut oil in a large pot over medium heat. Add the onion and cook until it softens.
Stir in the garlic, ginger, and turmeric. Cook for one minute until the mixture smells fragrant.
Add the plantain slices and cook for two to three minutes, stirring once.
Pour in the black beans, coconut milk, and vegetable broth. Bring the soup to a simmer.
Simmer for 15 to 20 minutes until the plantains turn tender.
Stir in the lime juice and season with salt and black pepper.
Ladle into bowls and top with chopped cilantro before serving.