Brown the Pumpkin: In a large skillet or pot, heat 2 tablespoons of olive oil over medium heat. Add the pumpkin cubes and season with salt and pepper. Cook for 10-12 minutes, stirring occasionally, until the pumpkin is browned and slightly caramelized. Remove the pumpkin from the pot and set aside.
Prepare Aromatics: In the same pot, add the cumin seeds and cook until fragrant, about 1 minute.
Cook Onions and Spices: Add the sliced red onion to the pot and cook until soft and translucent, about 5 minutes. Add the minced garlic, grated ginger, and sliced red chili. Stir in the red curry paste and cook for another 5 minutes, stirring frequently to prevent burning.
Add Spices and Liquids: Stir in the turmeric, ground coriander, garam masala, and ground cardamom. Cook for about 1 minute until fragrant. Add the peanut butter, chopped tomato, and vegetable broth (if needed to adjust consistency). Mix well.
Simmer with Coconut Milk: Pour in the coconut milk and return the browned pumpkin to the pot. Stir gently to combine and bring the mixture to a gentle simmer. Cook for about 5 minutes, allowing the flavors to meld together.
Serve: Serve the curry hot over rice. Accompany with naan bread and sprinkle with cashews if desired.