Heat oil in large pot over medium; sauté onion 4-5 minutes until soft and translucent.
Add garlic and ginger; stir constantly about 1 minute until fragrant.
Add sweet potatoes and carrot; stir to coat. Add turmeric and optional cayenne; stir another minute.
Add broth; boil, reduce to medium-low, cover, and simmer 20-25 minutes until potatoes fork-tender.
Off heat, immersion-blend silky smooth or carefully transfer hot liquid to regular blender in batches.
Add coconut milk, honey, and lime juice; season with salt and pepper. Gently heat 2-3 minutes; serve warm with toasted pumpkin seeds and cilantro.