Preheat your oven to 375°F (190°C).
Cut the top off the pumpkin and scoop out seeds and fibers.
Generously spread butter or tallow inside the pumpkin cavity.
In a large skillet, melt a little more butter or tallow. Sauté diced onion until translucent.
Add walnuts and sauté for 2 minutes.
Add cauliflower florets, cinnamon, salt, pepper, and raisins. Fry everything together for 5-7 minutes until just golden and fragrant.
Fill the pumpkin cavity with the cauliflower mixture.
Replace the top and place the stuffed pumpkin on a baking tray. Bake for 1 to 1.5 hours, until the pumpkin flesh is fork-tender.
Allow to cool slightly, then cut open, peel away the pumpkin skin, dice the pumpkin flesh, and mix it with the stuffing.
Serve warm.