Preheat oven to 400F.
Wash and rub sweet potatoes. Poke a few wholes with a knife in each potatoes then place on a baking sheet. Bake in preheat oven until very tender, about 45 to 50 minutes. Put sweet potatoes aside from heat and turn off oven.
Cook lentils in water or broth according to package directions. Set aside.
In a large skillet, heat olive oil over medium heat. Add cumin seeds and let them cook, stirring, for about a minute. Then, add onions and cook until softened, about 3 minutes.
Add tomatoes, garlic, ginger, salt, paprika, coriander, cinnamon and pepper, and cook, stirring often, for about 5 minutes.
Add in lentils, stir again and let cook for a few more minutes before adding spinach and turning off heat. Set aside.
To make the sauce, add tahini, water, lemon, maple syrup, garlic, salt and pepper in a small blender and blend until silky smooth.
Cut the sweet potato lengthwise with a knife and gently open the potatoes. Fill with lentils, drizzle with sauce and top with fresh herbs. Serve.