This fish gets its Middle Eastern tang from zaatar, a spice blend that's having a big moment, and its sesame-rich sauce. A fine side dish: oven-roasted diced potatoes (start them before the fish) tossed with parsley and olive oil. Couscous would be good too.
1. Set rack in top third of oven and preheat to 450°. Zest half of 1 lemon into a small bowl. Add zaatar, cumin, chile flakes, 1 tsp. salt, 1/4 tsp. pepper, and the oil; mix. Coat one side of fillets with paste.
2. Arrange halibut, paste side up, on a baking sheet and set on upper rack. Roast until fish is just cooked through, 6 to 10 minutes.
3. Put tahini, garlic, 2 tbsp. water, juice of 1/2 lemon, and remaining 1 tsp. salt and 1/4 tsp. pepper in a blender and whirl until smooth and pourable. Add more lemon juice to taste, and more water if you'd prefer a thinner sauce. Cut remaining lemon into wedges.
4. Serve fish with tahini sauce and lemon wedges.
*Find zaatar, a Middle Eastern spice blend of sesame seeds, sumac, thyme, and oregano, in your grocery store's spice aisle.
Wine pairing: A silky red like Crossbarn by Paul Hobbs 2012 Pinot Noir (Anderson Valley; $35); aromatic spices echo zaatar. --Sara Schneider