Heat a large pot over medium heat. Add the oil, onion, bell pepper and mushrooms; cook for about five minutes, stirring frequently, until the onion is translucent.
Add the marinara sauce, vegetable broth, lentils and lasagna noodles; stir to combine. Reduce the heat and simmer for about 25 minutes, stirring frequently, until the lentils and noodles are tender.
Add the spinach and stir to combine. Ladle into four bowls and top each with a spoonful of ricotta or vegan cheese shreds. Garnish with fresh parsley and freshly ground black pepper, if desired.
