1 small, seedless watermelon (about 2 pounds), rind removed and cut into 1-inch cubes (about 5 cups), divided
2 tablespoons vegetable oil
1 teaspoon cumin seeds
3 cloves garlic, minced
1 teaspoon ground coriander
1/4 teaspoon ground turmeric
1/4 teaspoon ground cayenne pepper
1/2 teaspoon kosher salt
2 teaspoons coarsely chopped fresh cilantro
Steamed basmati rice, for serving
Purée 1 cup of the watermelon cubes in a blender or food processor until smooth; set aside.
Heat the oil in a large frying pan over medium-high heat until shimmering. Add the cumin seeds and cook until toasted and fragrant, about 30 seconds. Add the garlic and sauté until it just starts to brown, about 30 seconds.
Add the puréed watermelon, coriander, turmeric, cayenne, and salt. Reduce the heat to medium-low, simmer, and let the liquid reduce slightly and thicken, 3 to 5 minutes.
Add the remaining watermelon cubes to the pan. Toss them gently to coat so that they're evenly coated with sauce. Cover the pan and simmer until the watermelon is heated through, 3 to 5 minutes. Taste season with more cayenne and/or salt as needed.
Sprinkle with the cilantro and serve over rice. This curry does not keep well, so it's best eaten immediately.