Heat the oil in a large pot over medium heat. Add the onion and cook for 3 to 4 minutes until it softens.
Stir in the garlic and ginger, then add the curry paste and cook for 1 minute until fragrant.
Add the lentils, potatoes, red bell pepper, and vegetable broth. Bring the mixture to a boil.
Reduce the heat to low, cover the pot, and simmer for 25 minutes until the lentils and potatoes are tender.
Stir in the coconut milk and lime juice. Season with salt and black pepper to taste.
Ladle the stew into bowls and top with chopped cilantro before serving.