Curry powder is a complex spice blend associated with Indian cuisine. It's made from spices like turmeric, ginger, and cumin, which add a little kick and lend a warm mouthfeel.
The spice blend gives any dish an earthy flavor along with a bright yellow color, making it perfect for tuna salad. For each pound of tuna salad, use about 1 tablespoon of curry.
Acidity and sweetness add a great flavor contrast to curry powder, so liven up the salad with some fruit and use veggies like carrots and red onion to build texture and crunch.