Heat the large pot over medium heat and add a tablespoon of olive oil, swirling to coat the bottom.
Add the finely chopped onion and sauté until translucent and fragrant, about 5 minutes, until it begins to smell sweet and turns a light golden color.
Stir in the minced garlic and cook for about 30 seconds until it becomes fragrant, filling the kitchen with a warm aroma.
Add the chopped spinach to the pot and cook, stirring occasionally, until wilted and vibrant green, about 2-3 minutes. The spinach should be tender but not mushy.
Pour in the vegetable broth and bring the mixture to a gentle simmer. Let it cook for about 10 minutes to allow flavors to meld and spinach to soften further.
Remove the pot from heat and use an immersion blender or transfer the soup in batches to a blender. Puree until silky smooth, about 1 minute, stopping to scrape down the sides as needed.
Stir in the heavy cream and warm the soup gently over low heat—avoid boiling to prevent curdling. Taste and adjust seasoning if needed.
Mix in the lemon juice to brighten the flavor, giving the soup a fresh, zingy finish. Briefly blend or stir to combine.
Spoon the hot soup into bowls, and optionally garnish with a drizzle of olive oil or a sprinkle of Parmesan cheese. Serve immediately while steaming hot.
