* 3 medium blood oranges (If not available, substitute 2 large, juicy navel oranges)
* 2 tbsp olive oil
* 2 cups finely chopped onions
* 1½ tsp fresh ginger, peeled and finely minced
* About 1 tbsp orange blossom or other light floral honey
* Salt and freshly ground black pepper
* 1 pound rhubarb, trimmed, fibrous strings removed with a vegetable peeler
* 1 cup fresh orange juice
* generous pinch of cinnamon
* 2 cups (about 1 pound) canned, peeled plum tomatoes, coarsely chopped, and ½ cup of their liquid
* Juice of ½ lemon
* 3 pounds fish fillet or steaks (choose salmon or white-fleshed fish like red snapper, grouper, sea bass, halibut, cod, lemon or grey sole)
* If steaming the fish, mild lettuce or cabbage leaves
Garnish: ¹\³-¹\² cup finely minced fresh mint leaves
1. start the sauce. With a vegetable peeler, remove a long strip of zest from one of the oranges. Put it in a small saucepan with water to cover, and bring to a boil. Drain, rinse, and pat it dry. mince the zest fine. Peel 2 of the blood oranges (or 1½ of the naval oranges), removing all of the bitter white pith and any seeds. Slice the oranges into chunks using a serrated knife. Set the orange zest and chunks aside. (You will be using the remaining blood orange, or half navel orange, to garnish the finished dish.)
2. In a 10-inch heavy skillet, warm the oil over moderate heat. Add the onions, and cook, stirring, for 5 minutes until they are shiny and lightly softened. Add the minced orange zest, ginger, and 1 tsp of the honey. Sprinkle lightly with salt and pepper. Continue cooking over low heat, stirring occasionally, until the onions are pale gold and very soft and sweet,15-20 minutes.
3. While the onions are cooking, prepare the rhubarb. Cut it into 1-inch chunks and place it in a medium saucepan. Add ½ cup of the orange juice, the remaining 2 tsp of honey, the cinnamon, and a pinch of salt. Bring the mixture to a boil, then simmer, stirring occasionally, until the rhubarb is very tender, 6-8 minutes.
4. When the onions are ready, add the remaining ½ cup orange juice to the skillet and boil the mixture, stirring and scraping it so it does not burn, for 3-4 minutes, until the liquid evaporates and the onions are deep golden. Stir in the tomatoes and their liquid and cook over moderately high heat until they break up, about 10 minutes. Add the rhubarb mixture to the sauce, and cook over moderate heat for 5 minutes. Add the reserved orange chunks, and simmer for 5-7 minutes, until the sauce is thickened and the flavors well-blended. Season to taste with salt and pepper and some of the lemon juice. Taste again and, if needed, add additional honey or lemon juice until you reach your perfect sweet-and-sour balance.
5. Let the sauce cool to room temperature, then cover and refrigerate it for at least 12 hours or up to three days to blend the flavors.
6. Prepare the fish, either poaching or steaming it.
To poach the fish: in a deep, lidded skillet or saut