1. Heat butter in a medium pot over medium heat. Add scallions and salt and cook, stirring occasionally, until tender, 6 to 8 min. Add 2-1/2 cups water and bring to a boil.
2. Reserve 1/2 cup of the peas and add the rest to the soup. Reduce heat to a simmer and cook 5 to 6 min.
3. Puree soup in batches until smooth; stir in lemon juice. Garnish with reserved peas. Makes 4 servings.