Heat the oil in a large skillet over medium-high heat.
Add the onion, garlic, and ginger, and cook until the onion is softened, about 5 minutes.
Add the cumin, coriander, curry powder, chili powder, turmeric, and garam masala, and cook for 1 minute, stirring constantly.
Stir in the diced tomatoes and water, and bring to a boil.
Add the tilapia fillets, and reduce the heat to medium-low. Simmer, uncovered, until the fish is cooked through and flakes easily with a fork, about 10 minutes.
Season with salt and pepper to taste, and serve hot.
Interesting Facts
Kerala is a state on the southwestern coast of India.
Tilapia is a mild-flavored white fish that is often used in Indian cooking.
Curry powder is a blend of spices, typically including cumin, coriander, turmeric, chili powder, and garam masala.