Heat the olive oil in a large pot over medium heat.
Add the onion and carrots and cook for 5 minutes until softened.
Stir in the garlic and ginger and cook for 30 seconds.
Add the curry powder, cumin, and turmeric.
Cook for 1 minute until fragrant.
Stir in the red lentils, vegetable broth, and diced tomatoes.
Bring to a boil.
Reduce the heat and simmer for 20 to 25 minutes, stirring occasionally.
Cook until the lentils are very soft.
Use an immersion blender to blend part of the soup if desired.
Stir in the salt, pepper, and lemon juice.
Serve hot and garnish with fresh cilantro.