Heat a medium pot over medium heat and add the olive oil. Once shimmering, add the diced onion and sauté for 5-7 minutes until translucent and fragrant, stirring occasionally.
Add the fresh peas to the pot and cook for 2 minutes, allowing their aroma to deepen and their color to brighten.
Pour in the vegetable broth and bring the mixture to a gentle simmer. Cover loosely and cook for 8-10 minutes, until the peas are tender and the soup is vibrant green.
Remove the pot from heat and use an immersion blender to purée the soup until smooth and silky, or carefully transfer to a blender in batches and blend until creamy.
Stir in fresh lemon juice, starting with half a lemon, and taste. Adjust salt and pepper as needed, and add more lemon for brightness if desired.
Ladle the soup into bowls, garnish with chopped fresh herbs if you like, and serve immediately while warm and velvety.
