This is a non-traditional interpretation of a Northern Indian dish called Aloo Gobi (potatoes and cauliflower). Even my Indian husband admits that though my roasted version of this favorite doesn't bear much resemblance to his mother's dish, it's still pretty tasty. You'll find black mustard seeds (they are sometimes dark brown) in high-quality markets and any Indian grocery store. If you can't find them, just omit. Don't substitute yellow mustard seeds--they don't taste the same. —Ann S
Preheat oven to 400 degree F. Remove the leaves and core of the cauliflower. Cut cauliflower and potatoes into pieces of similar size--about 1 inch in length.
Cut onion in half through the stem and root ends. Cut halves into 1/4 inch wide wedges.
Toss vegetables with salt, spices and just enough oil to lightly coat. Spread across a rimmed baking sheet in a single layer. Roast for about 40 or more minutes, until vegetables are tender (test by piercing with a fork) and golden brown in spots. Turn vegetables twice during cooking so that they brown evenly on both sides. Taste for salt and add more as needed.