PREHEAT the oven to 425°F (220°C).
COOK pasta until al dente, drain and reserve in a large bowl.
HEAT canola oil in a large sauté pan, add pepperoni and brown on both sides. Remove pepperoni with a slotted spoon and toss with cooked pasta, leaving some of the oil in the sauté pan behind.
Add onions and garlic and cook until slightly golden. Add mushrooms and green pepper and cook for 2-3 minutes.
Stir in tomato sauce, paste, cooked lentils, oregano, basil, and red pepper flakes. Season with salt and black pepper. Stir into cooked pasta mixture.
MIX 1 cup (250 mL) grated cheese into the pasta mixture. Pour into prepared pan and sprinkle olives and remaining cheese over top.
BAKE uncovered for 20 minutes or until bubbly and lightly golden on top. You can use the broiler for additional browning. Set aside for 5 minutes to rest.
GARNISH with fresh basil and serve.
