This one-pan baked flounder recipe with garlic, Parmesan cheese, and vegetables is easy and so delicious (thanks to a bold and lemony sauce with Mediterranean spices!). If you can't find flounder, any mild white fish would work, such as Dover sole, halibut, or branzino filet will work. Choose thinner fish filets if possible. Serve baked flounder with potatoes or greens like broccoli or a green bean salad.
Pat the fish dry and season it well with kosher salt and black pepper on both sides. Arrange the fish in a large pan and add the zucchini and onions next to it and season them with salt and pepper.
In a small mixing bowl, add the garlic, spices, lemon juice, and olive oil. Whisk to combine.
Pour the sauce all over the fish and vegetables.
Bake in the heated oven for 7 to 10 minutes, then carefully remove the pan and sprinkle the grated parmesan all over the fish and vegetables. Return the pan to the oven and bake for another 3 to 5 minutes or so until the fish is flaky and the cheese has melted some. (Flounder fillets are thin and should not take too long to cook. Be careful not to overcook them).
Substitutes for flounder: Branzino, halibut, sole, cod, trout, snapper, or haddock -- any mild white fish would work. Just be sure to use thin fish filets.
Tip for success: Flounder fillets cook very quickly, so check after it has been baking for 7 minutes or so. If you find that the fish is cooking faster than expected, add the Parmesan sooner to give it some time to melt.
Can you use frozen flounder in this recipe? Yes, just be sure to thaw it overnight in the fridge. And pat it dry to remove excess moisture.
Leftovers and storage:Store leftovers in an airtight container in the fridge for up to 2 days. I prefer to eat leftover fish at room temperature. But you can add everything to a skillet over medium-low heat for a few minutes until just heated through.