Bring a large pot of water to a boil. Add sweet potato; cook until tender when pierced with a fork, 15 to 20 minutes. Drain and cool until easily handled, 5 to 10 minutes. Peel potato and mash with a fork.
Heat oil in a large skillet over medium heat. Add onion; cook and stir until browned, about 5 minutes. Stir in broth and garlic; cook, stirring occasionally, until onion is very tender, about 3 minutes.
Combine mashed potato, onion mixture, milk, parsley, basil, onion powder, cumin, and cinnamon in a blender; puree until smooth.