Set the oven to 220C/425F/gas mark 7. First, make the chermoula. Swirling constantly, toast the cumin in a dry pan over a medium heat until the first few seeds begin to pop and emit a savoury aroma – about 3 minutes.
Remove from the heat. Grind finely right away with a pinch of salt in a pestle and mortar or spice grinder.
Blitz the cumin with the rest of the chermoula ingredients. Taste and adjust the salt and acidity. Thin with water to your desired consistency. Cover and refrigerate until needed.
Slice each half of the squash crosswise into 15mm-thick crescents and put in a large bowl. Toss with enough olive oil to coat – about 6 tbsp. Season and put in a single layer on a baking sheet.
Bake until tender and caramelised – about 25-30 minutes, but check after 12. Rotate the sheets and switch their positions to ensure even browning.
Serve warm or at room temperature on a platter, drizzled with chermoula.