Rinse the red lentils under cold water until the water runs clear, to remove any debris and excess starch.
In a large pot, heat the olive oil over medium heat. Add the chopped onions and carrots, and sauté until the onions are translucent, about 5 minutes.
Stir in the minced garlic, cumin, paprika, black pepper, and a pinch of salt, cooking for an additional minute until fragrant.
Pour in the vegetable broth and add the rinsed lentils. Increase the heat to bring the mixture to a boil.
Once boiling, reduce the heat to a simmer, cover the pot, and let cook for about 20 minutes or until the lentils are soft.
Add the chopped spinach and continue to simmer for another 5 minutes, or until the spinach is wilted and tender.
Remove the pot from the heat and stir in the fresh lemon juice.
Using an immersion blender, blend the soup until it reaches a smooth consistency. If you prefer a chunkier soup, you can blend it less or leave it as is.
Taste and adjust the seasoning with additional salt, if necessary.
Serve hot, garnished with fresh mint if desired.