Preheat the oven to 375°F (190°C).
Cook the pasta in salted water until al dente (slightly firm). Drain and set aside.
While pasta is cooking, heat oil and butter in a large pan over medium heat.
Add minced garlic and sauté until fragrant, about 30 seconds.
With a whisk, stir in the flour and cook for another 1 minute or so until it’s like a paste.
Gradually whisk in the milk to create a smooth white sauce. Cook for 3-4 minutes, stirring constantly, until thickened.
Stir in the lemon zest, juice, oregano, basil, chili flakes (if using), salt, and pepper. Adjust seasoning to taste.
In a large mixing bowl, combine the cooked pasta, lentils, chopped vegetables, and the lemon sauce. Toss until well coated.
Transfer the mixture to a greased baking dish.
Sprinkle with mozzarella and Parmesan.
Bake in the preheated oven for 20-25 minutes, or until the cheese is melted and bubbly. Garnish with fresh herbs (like parsley or basil) and an extra squeeze of lemon juice if desired. Enjoy!