Heat oil in large, heavy-bottom saucepan set over medium heat; add onion, carrot, celery, garlic, salt, pepper, oregano and smoked paprika. Cook, stirring often, for 3 to 5 minutes or until softened.
Stir in lentils; cook for about 2 minutes or until well coated. Stir in strained tomatoes. Simmer, stirring occasionally, for 15 to 20 minutes or until thickened.
Meanwhile, during last 10 minutes of cooking time for sauce, cook spaghetti in large pot of boiling salted water according to package directions. Drain well, reserving 1/3 cup (75 mL) pasta water. Toss spaghetti with sauce, reserved pasta water and parsley.
Substitute basil for parsley if desired.Top with grated vegan cheese if desired.