Heat the olive oil in a large pot over medium heat. Once hot, add the diced onion and sauté until it begins to soften, about 3-4 minutes.
Add the minced garlic, tomato paste, dried basil, and oregano to the onions. Continue to cook, stirring frequently, until the mixture is fragrant and the onions are fully translucent, about 2-3 minutes.
Pour in the crushed tomatoes and vegetable broth, then add the rinsed lentils. Increase the heat to bring the soup to a boil, then reduce to a simmer and cook for 10 minutes, or until the lentils are just starting to become tender.
Break the lasagna noodles into roughly 2-inch pieces and add them to the pot. Let the soup simmer for another 10-15 minutes, or until the noodles are cooked to al dente and the lentils are fully tender.
Stir in the fresh spinach and cook just until it wilts. Serve the soup hot, garnished with thinly sliced fresh basil.