Mix all ingredients except salt in a small bowl until lime juice is incorporated. Season with salt. Cover; keep in a cool place. DO AHEAD Spiced butter can be made 1 week ahead. Roll into logs, wrap in parchment paper, and refrigerate for up to 2 weeks or freeze for up to 3 months.
Trim ends of acorn and kabocha squash and cut in half through the stem end. Scrape out seeds and place squash cut side down on a cutting board (do not peel). Cut halves crosswise into 1/2-inch slices. If using delicata squash, cut crosswise into 1/2-inch rings; scrape out seeds.
Fill a large wide pot with water to a depth of 1 inch and add a pinch of salt; bring to a boil. Place squash in a large steamer basket over water; reduce heat to medium-low. Cover and steam, adding more water as needed to maintain 1/2-inch of water at bottom of pot, until squash is tender but not falling apart, 15 to 18 minutes.
Carefully transfer squash slices to a large platter (some squash at bottom of pot may be too soft; save for another purpose) and season with salt.
Reduce water in pot over high heat (or add hot water) to measure 3/4 cup. Remove from heat and whisk in spiced butter, 1 tablespoonful at a time, to form a rich, glossy sauce. Season to taste with salt. Drizzle spiced butter over squash. Top with pomegranate seeds.
9 servings, 1 serving contains:
Calories (kcal) 170
Fat (g) 10
Saturated Fat (g) 6
Cholesterol (mg) 25
Carbohydrates (g) 19
Dietary Fiber (g) 3
Total Sugars (g) 9
Protein (g) 3
Sodium (mg) 55