Adjust oven rack to upper-middle position and preheat oven to 425 degrees Fahrenheit.
In a large saucepan, add potatoes and 10 cups of water. Bring to boil on high heat and cook for 20 minutes over medium-high heat or until cooked through.
While the potatoes are cooking, start to prep the lentils filling. Begin by gathering all the ingredients to save time.
In a cast iron or another type of non-stick cooking pot, heat 1 tbsp of olive oil on medium heat.
Add the onion seeds, garlic and ginger and fry until golden.
Stir in the onions, cover and cook for 2-3 minutes on low heat to soften the onions. This technique helps to use less oil.
Pour in the tomato coulis along with the chopped peppers, dried fenugreek and red chilli powder. Feel free to go easy with the chilli to suit your taste preferences. Stir well.
Follow with the drained uncooked lentils and 2.5 cups of water. Stir, bring to boil over high heat and cover and cook for 15 minutes on medium-low heat. If you're using cooked lentils (canned), you don't need to boil and cook them and will need to reduce the amount of water.
Add 1 tsp of salt and juice of half a lemon and stir. You should end up with a thick (not dry) consistency. Transfer to a 12 X 8-inch rectangular baking dish or pan.
Right about now, the potatoes should be done. Drain and transfer to a large container.
Add 1/2 tsp salt, 1 tsp of pepper and 1 tsp of parsley flakes to brings flavour to the potatoes without the need for added fat and more salt. Mash the potatoes thoroughly.
Now spread the mashed potatoes evenly over the filling. I like to do this in small batches to keep the two layers intact. Brush 1 tbsp of oil all over the potato topping.
Bake for 10 mins and broil about 1-2 minutes until the top is golden. You don't want to overdo this as the potatoes will dry out.
Remove from oven and cool for 5-10 minutes before serving. I like to garnish with more parsley flakes - just because!