Heat the olive oil in a large pot over medium heat. Add the chopped onion and cook for 5 minutes until it softens.
Stir in the minced garlic and curry powder. Cook for 1 minute until the spices smell fragrant.
Add the rinsed red lentils, broccoli florets, vegetable broth, and salt to the pot. Bring the mixture to a boil.
Reduce the heat to low, cover the pot, and simmer for 20 minutes until the lentils are soft and the broccoli is tender.
Remove the pot from the heat. Use an immersion blender to puree the soup until smooth and creamy.
Stir in the lemon juice. Taste and adjust salt if needed.
Ladle the soup into bowls and top with fresh cilantro before serving.