Add the garlic and toss. Cook for 1 minute. Add the ground cumin, ground coriander, turmeric and paprika (or cayenne). Toss and less the spices briefly roast. Then add the potatoes with another hefty pinch of salt. Toss with onions and spices briefly, then add the tomatoes, water, split peas and split lentils. Bring to a boil and then place a lid on the pot, reducing the heat to maintain a gentle simmer. Let simmer for 20 minutes.