Trim and chop the asparagus, ensuring that the tough ends are removed.
Set the tips aside for garnish later.
In a large pot, melt the butter over medium heat.
Add the chopped onion and cook until softened.
Add the chopped asparagus (excluding tips) to the pot along with the chicken broth.
Simmer for about 15 minutes or until the asparagus is tender.
Using a blender or immersion blender, puree the soup until smooth.
Return the soup to the pot.
Stir in the cream, salt, black pepper, and lemon juice.
Simmer for an additional 5 minutes.
Serve warm and garnish with the reserved asparagus tips.