Add the carrots and celery and cook for a further 3 minutes. Then stir in the red lentils and the tomato paste. After another minute, deglaze with red wine and allow to evaporate (this will take about 1 minute).
Add the diced tomatoes and vegetable broth and simmer for about 15-20 minutes until the sauce is thick and the lentils are fairly soft and good to eat (they shouldn't be too soft).
Season with the Italian spices, salt, and pepper and - if using - soy sauce. Serve together with the spaghetti and sprinkle with some fresh basil leaves.