1. Bring 2 quarts of water to a boil, then add the red potatoes. Boil as you would for potato salad, reducing heat to a high simmer and cooking until fork tender (but not mushy!), usually about 20 minutes. Drain the pot and rinse the potatoes until they're cool to the touch.
2. While the potatoes are cooking, bring a second smaller pot of water to a boil for the cauliflower. Combine the curry powder and coriander with 1 tablespoon water, let stand for a few minutes. Cook the cauliflower 3 minutes, rinse, and drain.
3. Peel the skin off the potatoes and cube. Heat the margarine or oil over medium-high heat. Add the onion, mustard seed, and cumin seeds. When the seeds start to sizzle and pop, add the curry/water mix, stirring well to evenly coat the onions.
4. Cook 3 minutes, then add the lemon juice, along with the potatoes and cauliflower, stirring well to coat. Add the cilantro and peppers, along with 1/2 cup water, turn the heat down a bit and simmer until the veggies are heated through and the sauce is thick-about 10 minutes. Season, to taste.
Serve over saffron rice!