Preheat the oven to 400 degrees F. Line a baking sheet with aluminum foil.
In a small bowl, pour enough boiling water over the cashews to cover; set aside to soften, at least 45 minutes.
Meanwhile, in a bowl, stir together the cauliflower, onion, garlic, about ½ teaspoon salt, and the oil, turning to coat evenly. Scrape onto the baking sheet and roast in the center of the oven until the cauliflower is completely tender when the tip of a knife is inserted, 20 to 25 minutes, stirring once or twice. Carefully sprinkle on the curry powder and cumin, stir, and roast for 2 minutes longer.
Strain the cashews, rinse under cold water, and transfer them to the jar of an electric blender. Add the stock and purée on high until completely smooth.
Scrape the cauliflower mixture into the blender, add the coconut milk, honey, and cayenne if using, and purée until completely smooth, scraping down the sides as needed. Taste to adjust the salt, if needed.
Scrape into a clean container, cover, and refrigerate for 30 minutes to 1 hour. Ladle into bowls, sprinkle on the pomegranate seeds if using, add the cilantro, and serve.