Heat the olive oil in a large pot over medium heat. Add the onion, carrots, and celery. Cook for 5 minutes until the vegetables soften.
Stir in the garlic, cumin, turmeric, cinnamon, and ginger. Cook for 1 minute until the spices smell fragrant.
Add the diced tomatoes and vegetable broth. Bring the mixture to a simmer.
Stir in the rinsed red lentils and chickpeas. Cover and cook for 20 minutes, stirring occasionally, until the lentils break down and thicken the soup.
Remove the pot from the heat. Stir in the lemon juice and chopped cilantro. Season with salt and black pepper to taste before serving.