Begin by dicing the sweet potatoes and onions. Rinse the lentils thoroughly.

In a pan, heat olive oil over medium heat, and sauté the onions and garlic until translucent.

In your slow cooker, combine the sautéed onions and garlic with sweet potatoes, lentils, vegetable broth, diced tomatoes, chili powder, cumin, salt, and pepper.

Stir well to incorporate all ingredients.

Cover and cook on low for 6-8 hours or high for 3-4 hours, until sweet potatoes and lentils are tender.

Serve warm, optionally garnished with fresh cilantro or avocado.