Heat the oil in a large skillet over medium heat. Add the diced onion and cook until soft and lightly golden, then stir in the garlic and grated ginger until fragrant.
Mix in the red curry paste, turmeric, cumin, and coriander. Cook for about a minute, stirring constantly so the spices become aromatic without burning.
Add the pumpkin cubes and stir well until they are evenly coated with the spice mixture.
Pour in the coconut milk and vegetable broth, then stir in the soy sauce and brown sugar. Bring the curry to a gentle simmer.
Cover the pan and cook until the pumpkin is fork-tender and the sauce has naturally thickened, stirring occasionally to prevent sticking.
Finish with fresh lime juice and season with salt and black pepper to taste. Sprinkle with chopped cilantro and serve warm over steamed jasmine rice.