Bring a large pot of salted water to a boil. Add the pasta and cook just until tender, or somewhat al dente. Drain and rinse the pasta with cold running water. Set aside.
Preheat the oven to 350°F then lightly grease a 9x13” baking dish.
In the same pot, warm the oil over medium heat. Add the onion, jalapeño and red bell pepper then cook for 5 minutes, until soft.
Next, add the mushrooms, garlic, chili powder, oregano, and smoked paprika. Continue to cook for about 3 minutes, stirring intermittently.
Lastly, pour in the diced tomatoes, tomato paste and cooked lentils. Stir to combine. Cook over a low simmer until the mushrooms are tender, about 5 minutes. Remove from heat then stir in the cooked pasta.
Transfer the lentil mixture to the greased casserole dish. Spread cheese sauce over top and out to the sides. Garnish with smoked paprika, diced tomatoes, and red onion. Bake in the oven for 15-20 minutes, until heated through. Serve warm and enjoy!