A short dry toast is one of the simplest ways to get more out of whole cumin seeds. Heat releases the aromatic essential oils, so the seeds become richer and more expressive, and the warm, earthy, slightly nutty character comes through more clearly.
To toast them at home: put a small dry pan over medium heat with no oil. Add the seeds in a thin layer so they heat evenly, and shake or stir them gently. They only need a minute or two. You will know they are done when they darken a shade and the smell of cumin fills the air. Tip them onto a plate right away; if they stay in the hot pan, the residual heat will keep cooking them.
Toasted seeds can be used whole, added to a dish for a richer aroma, or cooled briefly and ground. Toasted and then ground cumin has a deeper profile that works especially well in spice blends, marinades, dressings and dips. Grinding right after toasting gives the most vivid result.
The main thing to watch is time. Cumin seeds go from fragrant to bitter very quickly if they burn, and bitterness cannot be fixed once the seeds are in the dish. Toast in small amounts and use them soon after, because even whole toasted seeds lose strength as time passes.