Delicious Baked Haddock: A Flavorful Spinach and Tomato

Preheat the oven to 375 degrees F (190 degrees C). Lightly butter a 2-quart casserole or baking dish large enough to hold haddock fillets in a single layer.

Melt butter in a skillet over medium heat. Cook and stir onion in hot butter until soft, about 5 minutes. Stir in spinach and nutmeg; cook, stirring occasionally, for about 3 minutes.

Arrange haddock fillets in the prepared baking dish. Spoon equal portions of spinach mixture between fillets. Spoon drained tomatoes around fillets and sprinkle with thyme, salt, and tarragon.

Bake, uncovered, in the preheated oven until fish flakes easily with a fork, 20 to 25 minutes.

While fish is baking, make sauce: Add enough water to reserved tomato juices to make 1 cup; set aside. Melt butter in the skillet over medium heat. Stir in onion and cook until soft, about 5 minutes. Pour 3/4 cup tomato juice into the skillet; bring to a boil. Whisk cornstarch into remaining 1/4 cup tomato juice, then add to the skillet. Reduce heat and simmer, stirring, until sauce thickens slightly.

Pour sauce over baked fillets and serve.