Heat the olive oil in a large pot over medium heat. Add the diced onion and carrots and cook for 3 minutes until the onion softens.
Stir in the minced garlic along with the cumin, coriander, turmeric, and cinnamon. Cook for 1 minute until the spices become fragrant.
Add the rinsed red lentils, vegetable broth, and diced tomatoes with their liquid. Bring the mixture to a boil.
Reduce the heat to a simmer and cook uncovered for 15 to 18 minutes, stirring occasionally, until the lentils are tender.
Remove the pot from the heat. Stir in the lemon juice and season with salt and pepper. Ladle into bowls and top with chopped cilantro.