4 spring onions or large scallions, bulbs separated from tops
2 tablespoons olive oil, divided
¾ pound assorted summer squash (2 small), cut into 1-inch pieces
1½ teaspoons thyme leaves plus 2 sprigs
Kosher salt and freshly ground black pepper
2 6-ounce skinless halibut fillets
Cut onion bulbs in half lengthwise. Cut the tops/dark green parts into 2-inch pieces to measure ½ cup. Heat 1½ teaspoons of oil in a large skillet set over medium-high heat. Add the bulbs, cut side down, and cook until golden, about 3 minutes. Transfer to a plate and set aside.
Add about another 1½ teaspoons of oil to the skillet. Add the squash and cook, stirring occasionally, about 5 minutes or until golden brown and tender. Add the onion tops and cooked onion bulbs and the 1½ teaspoons of fresh thyme. Cook for an additional minute, or until the onion tops are slightly wilted. Transfer vegetable mixture to a plate.
Heat remaining tablespoon of oil in the skillet. Season the halibut with salt and pepper. Add to the skillet, along with the sprigs of thyme, and cook until the fish is golden brown, about 5 minutes. Flip and continue cooking about 2 minutes, or until the fish is cooked through and opaque in the center. Divide vegetable mixture among plates and top with halibut. Serve immediately.