In a small saucepan (with lid) heat oil and add onion. Sauté until translucent and starting to brown. Add garlic and continue cooking until garlic is fragrant. Add spices, tomato purée and lentils. Turn to low, cover and cook until lentils are al dente, about 20 minutes. Be careful not to over cook.
Preheat oven to 350 degrees. Prepare baking sheet with parchment paper and top with a layer or tortilla chips overlapping them to cover parchment completely.
Spread lentils, peppers, and tomato over tortilla chips. Grate avocado directly on top of nachos. as it may clump together a little. Top with cheese, distributing it evenly.
Bake for 5-7 minutes until hot. Change oven to low broil and place under the broiler for a few minutes to make cheese bubbly and slightly toasted. Watch carefully as this can happen fast! Top with cilantro, and serve immediately with your favourite salsa.