Cook, stirring occasionally, until onion is translucent, about 8 to 10 minutes. Add broth. Bring the mixture to a boil, then reduce heat and simmer until squash is soft, about 15 to 20 minutes.
Heat oil in a large Dutch oven or heavy-bottomed pot over medium heat. Once the oil is shimmering, add squash, onion, garlic, curry paste, coriander, cumin, salt and red pepper flakes to skillet. Stir to combine.