1. If starting with dried lentils, rinse the lentils in a fine-mesh colander to remove any dust or debris. Place the rinsed lentils in a medium saucepan and cover with 3 cups cold water. Add the whole clove of garlic, peeled, and the bay leaf. Bring the water to a boil over high heat.
2. Turn the heat down to low, cover the pan and simmer until the lentils are tender, but still holding their shape, 15 to 20 minutes. Drain the lentils and allow them to cool. (May be done up to one day in advance.)
3. Make the sauce: heat the olive oil in a large saucepan or Dutch oven over medium heat. When the oil is shimmering, add the diced onion and sauté for 5 minutes. Add the celery and carrots and sauté for an additional 5 minutes, until the vegetables are softened.
4. Add the minced garlic, oregano, salt, and red pepper flakes and stir to combine. Sauté an additional minute, just until fragrant.
5. Add the canned tomatoes with their juices, breaking up the tomatoes with your fingers or a wooden spoon, and sugar. Bring the sauce to a boil over high heat.
6. Then, reduce the heat and simmer until slightly thickened and reduced, about 20 minutes.
7. While the sauce is cooking, bring a large pot of salted water to a boil. Add the spaghetti and cook to al dente according to the package directions. Drain.
8. Add 2 cups of the cooked lentils (or the drained and rinsed canned lentils) to the tomato sauce and stir to combine. Taste and adjust seasoning, adding more salt if necessary. Simmer just until the lentils are heated through.
9. To serve, divide the spaghetti evenly among four plates or pasta bowls. Top with the tomato-and-lentil sauce. Garnish with torn or sliced basil leaves. Serve immediately.

Love this recipe? I’d appreciate it if you could scroll down and add a *5 star rating* to help others know they’ll love it as well!