Set a large deep skillet with a lid over medium heat so it is ready when the rice is rinsed.

Put the rice in a fine-mesh strainer and rinse it under cold water until the water runs mostly clear. Let the rice drain well.

Add the olive oil to the skillet and let it warm for about 30 seconds.

Add the chopped onion to the skillet. Cook for 5 minutes, stirring now and then, until it is soft and starting to turn pale gold around the edges.

Add the sliced garlic to the skillet. Stir for 30 seconds, just until it smells fragrant.

Add the drained rice to the skillet. Stir for 1 minute so the grains are coated in the oil and mixed with the onion and garlic.

Pour the diced tomatoes with their juices and the vegetable broth into the skillet. Stir well and scrape the bottom of the skillet so nothing is stuck.

Turn the heat up to medium-high and bring the liquid to a boil.

Lower the heat to low, cover the skillet, and cook for 12 minutes.

While the rice cooks, put the cod pieces on a plate. Rub the lemon zest over the fish and season it lightly with salt and black pepper.

Uncover the skillet and check the rice. It should be nearly tender, with a little moisture still visible on top. If the pan looks dry before the rice is nearly tender, add 2 tablespoons of water.

Nestle the cod pieces into the rice in a single layer, pressing them in just enough so they sit snugly on top.