Meanwhile, we peel and quarter the potatoes and thinly slice the carrots. We add these to the lentils, along with some salt, pepper, and another quarter cup of water to replenish the water we skimmed off. We lower the soup to a simmer, and partially cover for about 20 minutes.
While the soup is simmering, we chop the onion and mince the garlic with a little salt. In a pan, we heat the canola oil. We add the onions and cook on medium-low for about 5 minutes until translucent. Then we add the minced ginger and continue to cook for a few minutes. We add the garlic and stir for 30 seconds. Next, we add the cumin, coriander, turmeric and cayenne, and cook for another minute. We add a little water, about a tablespoon, and stir up the stuck-on spices. We remove the bay leaf and ginger slice from the soup pot and add the onion spice mixture. We cook on low heat for another 15 minutes. When we are ready to eat, we add the lemon juice, and taste for salt and pepper.
We garnish each bowl with cilantro and serve immediately.