Heat olive oil over medium-high heat in a large stock pot. Add the onion and sauté for 3 minutes, stirring constantly.
Add the carrots and sauté for an additional 3 minutes, until the carrots begin to soften. Add the garlic and sauté for 30 seconds, stirring constantly. Add basil through lentils and stir to combine.
Bring to a boil over medium-high heat, stirring occasionally. Turn heat to medium-low, cover and boil for 25-30 minutes, until the lentils are cooked through and the sauce has thickened.
Add salt, increasing amount to taste, if necessary. Place cooked pasta into a serving bowl, topped by sliced spinach, lentil ragu, and fresh parmesan cheese.