Heat olive oil in a pot over medium-low heat. Add onion and cook until translucent, about 5 minutes. Add sweet potatoes, carrots, garlic, garam masala, seasoned salt, cayenne pepper, salt, and pepper. Cook for 5 minutes. Add broth and water. Bring to a boil and cook until flavors start to blend, about 10 minutes.

Add spinach and lentils; bring to a boil. Reduce heat to low and simmer until lentils are soft, 15 to 20 minutes.