When to add cumin depends on whether you are using whole seeds or ground cumin. Whole seeds are often added to hot oil or ghee at the beginning of a curry to build a fragrant base. Ground cumin is usually stirred in after the aromatics have softened, then cooked briefly with the other spices so its flavour blends into the sauce.
Whole cumin: start with the tempering
Heat the oil or ghee over a moderate flame, then add whole cumin seeds. When they sizzle and smell fragrant, add the next ingredients, such as onion, ginger or garlic. This quick tempering releases the seeds' earthy aroma into the cooking fat. Watch them closely: if they turn very dark or burn, they can taste bitter.
Ground cumin: add it with the spice base
For ground cumin, wait until the onions or other aromatics are cooked as your recipe directs. Stir the powder in with the other ground spices and cook it briefly before adding tomatoes, stock or another liquid. Keep stirring and use a little moisture if the pan looks dry, because ground spices catch more quickly than whole seeds.
For a finishing touch
Some curries and dals are finished with toasted or roasted ground cumin. In this case, add a small amount near the end or just before serving so its aroma remains distinct. Whether this works best depends on the recipe and the taste you want.
Adjust to the curry
Cumin is used differently across Indian regional cuisines and family recipes. Some dishes rely on whole seeds, others on ground cumin, and many use both. Start with the recipe's suggested amount, taste as you cook and avoid adding cumin to very hot, dry oil where it can scorch.
As a simple guide: whole cumin goes near the beginning for a fragrant base; ground cumin joins the spice mixture during cooking; toasted ground cumin can be saved for the finish. Let the recipe decide which stage suits your curry.