Heat oil or vegetable broth in a large saucepan over medium-high heat.
Add onion and cook until soft, about 2 minutes.
Stir in garlic, ginger, bell pepper, green onion, and thyme. Cook until fragrant, about 1 minute.
Stir in tomato and cook for another minute.
Add curry powder, turmeric, cumin, allspice, and salt.
Stir in red lentils to coat with seasonings.
Add vegetable broth, coconut milk, and bring to a boil.
Cover saucepan then reduces heat to simmer until lentils are tender, about 15-20 minutes.