1. Peel squash and cut in half lengthwise. Remove and discard seeds. Cut squash into 1/2- to 3/4-inch cubes (you should have 2 1/2 cups).
2. In a 5- to 6-quart pan over medium heat, frequently stir onions, ginger, and garlic in butter until onions are very limp, 10 to 15 minutes.
3. Add rice and stir often until opaque, about 5 minutes. Add curry powder and stir for 30 seconds longer.
4. Stir in 1/2 teaspoon salt, squash, and broth. Bring to a boil over high heat; reduce heat, cover, and simmer, stirring occasionally, until rice and squash are tender to bite, 16 to 18 minutes. Stir in cilantro and salt to taste. Spoon into a bowl.