Ingredients

• 8 spring onions or large scallions, bulbs separated from tops
• 4 tablespoons (or more) olive oil, divided
• 1 1/2 pounds assorted summer squash, cut into 1" pieces
• 1 tablespoon thyme leaves plus 4 sprigs
• Kosher salt and freshly ground black pepper
• 4 6-ounce skinless halibut fillets

Instructions

1. Cut onion bulbs in half lengthwise (quarter if large). Cut enough onion tops into 2" lengths to measure 1 cup. Heat 1 tablespoon oil in a large skillet over medium-high heat until almost smoking. Add onion bulbs, cut side down; cook until golden, about 3 minutes. Transfer to a plate.
2. Heat 1 tablespoon oil in same skillet. Add squash; cook, stirring occasionally, until golden brown and just tender, about 5 minutes. Stir in onion bulbs, 1 cup onion tops, and 1 tablespoon thyme leaves; season with salt and pepper and cook until onion tops wilt, about 1 minute longer. Remove from heat; set squash mixture aside.
3. Heat remaining 2 tablespoons oil in a large nonstick or cast-iron skillet over medium-high heat. Season halibut with salt. Add fish and thyme sprigs to skillet and cook until fish is golden brown, about 5 minutes. Turn fish and cook until just cooked through and opaque in the center, about 2 minutes longer. Divide onion-squash sauté among plates; top with halibut.