How to Make It
In a large pot, melt the butter. Add the onion, garlic and chile and cook over moderately high heat until the onion is softened, 4 minutes. Add the cumin and cayenne and cook until fragrant, about 1 minute. Add the split peas and the water, then whisk in the pumpkin puree and bring to a simmer. Cover and cook over moderately low heat, stirring occasionally, until the split peas are tender, about 2 hours.
Stir the diced pumpkin into the soup and simmer over moderately low heat until tender, about 30 minutes. Remove from the heat. Stir in the lemon juice, season with salt and pepper and serve.