Step 1

Heat the oven. Preheat the oven to 400°F and position a rack in the middle.

Step 2

Make the sauce. In a large oven-safe pan or skillet, heat 2 tablespoons extra virgin olive oil over medium-high heat until shimmering. Add the sliced onions and season with a big pinch of kosher salt. Cook, tossing regularly, until the onions have softened and gained a slight golden-brown color (about 7 minutes). Add the garlic toss briefly, then add the canned tomatoes with their juices. Using a wooden spoon, break the tomatoes up. Season with a dash more salt. Add the oregano and a big dash of black pepper. Bring the sauce to a boil, then lower the heat and let it simmer for 10 to 15 minutes or so.

Step 3

Season the fish. Pat the fish dry and season on both sides with kosher salt, the oregano, paprika and cumin. Cut and squeeze one lemon over the fish (leave the other lemon for later).

Step 4

Combine the sauce and the fish. When the sauce is ready, nestle the fish in the sauce and scoop up some of the sauce to cover the top of the fish well.

Step 5

Bake. Place the fish on the center rack of the heated oven and bake until the fist turns opaque white and flakes easily at the touch of a fork (15 to 25 minutes, but because ovens do vary, it is a good idea to check occasionally to make sure the fish does not overcook or dry out).

Step 6

Serve. Slice the remaining lemon into wedges. Finish the fish with the fresh parsley and serve with the lemon wedges to the side.