Here’s the rub. Made of butter and vibrant spices, this rub is fragrant and bright, like inky yellow paint. The butter is a necessary fat—lamb is a lean animal. In a large bowl, stir together the butter, salt, ginger, cumin, turmeric, saffron, and garlic until well incorporated. Add the lamb and massage the spiced butter into the lamb, making sure to cover all of it well. Once your lamb is nicely coated, you can cover and refrigerate it overnight or proceed with the recipe.

Preheat the oven to 300°F. Heat the oil in a tajine or heavy pot over medium heat. Add the onions, season well with salt, and sweat until the onions release their liquid, about 20 minutes. Add the cumin, coriander, and pepper, stirring to let the spices bloom for about 10 minutes. This is the fragrance. Add the lamb, with all of its buttery rub, and the stock and bring to a simmer.

If you’re not using a traditional tajine, cut out a parchment paper round that’s the circumference of your pot and tear a nickel-size hole in its center. Place on top of the simmering stew. Cover the tajine or pot and slide it into the oven. Bake for 2 hours, then carefully remove the lid and parchment, if using. Add the squash, re-cover the tajine or pot, and bake for 1 more hour. Let cool at room temperature for 30 minutes. Just before serving, adjust the seasoning. Put the tajine in the center of the table, within reach of everyone.