Step 1

Preheat oven to 350°. Using a sharp heavy knife, halve squash lengthwise and scoop out seeds with a spoon (if desired, clean and use the seeds in Smashed Green Beans). Rub cut sides of squash with 1 Tbsp. oil and season generously with salt. Place cut side down on a rimmed baking sheet and roast until tender, 60–75 minutes.

Step 2

Scoop squash flesh from skin into a serving bowl. Using a potato masher or fork, smash until mostly smooth. Set aside a big spoonful of red onion and cilantro. Mix in chiles, ghee, coriander, cumin, chile powder, remaining red onion, remaining cilantro, and remaining 2 Tbsp. oil; season with salt and pepper.

Step 3

Top squash with reserved onion and cilantro just before serving.

Step 4

Do ahead: Squash can be baked and mashed 3 days ahead. Let cool; cover and chill.

Step 5

*Most mustard oils are not FDA-approved as edible in the United States due to their high erucic acid content. If you are concerned, look for Yandilla, an FDA-approved brand, online, or use olive oil instead.