Heat oven to 450°F. On large rimmed baking sheet, toss squash and onions with 2 tablespoons oil and ¼ teaspoon each salt and pepper. Roast until golden brown and tender, 25 to 35 minutes. Meanwhile, in bowl, whisk together tahini, lemon juice, water, and ¼ teaspoon salt, adding additional water if dressing is too thick. Toss squash with kale and arrange on a platter. Drizzle with dressing and sprinkle with lemon zest, cilantro, and almonds.