Rinse lentils and cook in a small saucepan with 1 cup of water until they just start to soften. This will take about 10 – 15 minutes. Add more water if needed.
Preheat the oven to 400˚F or 200˚C.
Peel the sweet potatoes and cut into bite-sized pieces. Sprinkle with cayenne, cumin, cinnamon, salt and pepper. Drizzle with olive oil and toss to coat, then spread out on a baking sheet. Roast for about 40 minutes or until soft and golden.
In the meantime, cut all other veggies.
Heat cooking oil over medium heat in a large pan. Sauté the onions for 2 minutes, add garlic, chili pepper, and bell pepper and cook until soft. Stir regularly.
Add zucchini and cook for another 5 minutes.
Then add tomatoes, water, and cooked/drained lentils. Give it a good stir, cover, and cook for about 30 minutes.
Add more water if needed and stir occasionally.
At the end, add roasted sweet potato.
Give it a good stir and serve with cashew or sour cream if using.