Preheat the oven to 420°F (215°C). In a large mixing bowl, toss in half of the olive oil, cauliflower florets, potatoes and a generous sprinkling of sea salt. Mix well and place onto a parchment paper–lined baking dish. Cook for 25 minutes or until the cauliflower and potatoes are tender. 

In the meantime, make the sauce. In a large skillet over medium heat, warm the remaining olive oil and all the spices, tomato purée and garlic. Let this simmer for a few minutes before adding the water. Add the water and let it warm for a few minutes. Now set the sauce aside until the cauliflower and potatoes have finished cooking. 

Once they’re done, bring the sauce back to the stove and add the roasted cauliflower, potatoes and lemon juice. Mix well, and warm over medium-high heat for about 5 minutes. Serve over a bed of rice or quinoa, and top with cilantro and sea salt.