Heat the oils in a large dutch oven over medium heat. When the oil heats, add the onion and cook for 3 to 4 minutes or until soft. Add the ginger, garlic, sweet potatoes, and red peppers and cook until fragrant, about 2 minutes.
Stir in the curry powder, cinnamon, and cumin. When the mixture is sizzling, add the chicken broth and or vegetable broth and the red lentils. Season with additional salt and add the red harissa. Bring the mixture to a boil over high heat, then reduce to a simmer.
Cover and simmer for 15 to 20 minutes, or until the lentils are soft and the sweet potatoes are tender. Add more broth if the mixture gets too thick.
Stir in the coconut milk and arugula and cook for 5 minutes. Remove from the heat and add the cilantro. Finish with the red pepper flakes and ground pepper.
To serve, divide the fluffy rice among bowls and ladle the soup over the top. Garnish with the cilantro.