Heat 2 tablespoons olive oil in a large sauté pan. Add onions and sauté 2 minutes. Stir in ginger, garlic, curry, cumin and coriander and continue cooking an additional 2 minutes, stirring occasionally.
Stir tomatoes into seasoned onions; break up tomatoes with a fork. Simmer tomatoes an additional minute and then stir in lentils.
Cook lentils in sauce until tender, about 35-45 minutes, stirring in 1/2 cup stock or water as needed to insure lentils don’t stick to pan, as you would do when making a risotto.
While lentils are simmering, bring a large pot of salted water to a boil for the pasta. Toss cauliflower florets with remaining 2 tablespoons of olive oil and arrange on a foil-lined baking sheet.
Roast cauliflower on middle-rack of oven 6-8 minutes or until florets are tender and golden brown. When lentils are tender, stir roasted cauliflower into the pan. For extra richness, if desired, stir ghee or butter into ragu. Season with cilantro and pepper flakes.
Boil pasta for five minutes, according to package instructions, and drain. Serve with Lentil-Roasted Cauliflower Ragu.
Leftover ragu keeps, refrigerated, for several days