Author Notes: From The New Persian Kitchen.

Parvin’s Tamarind-Stuffed Fish

Serves: 4

• 4farmed rainbow or brook trout, 8 ounces each, cleaned and butterflied
• Sea salt and freshly ground black pepper
• 5tablespoons grapeseed oil
• 1large yellow onion, thinly sliced
• 3cloves garlic, minced
• 1cup whole raw almonds, coarsely ground
• 1cup barberries, soaked in warm water for 1/2 hour and drained
• 1/4cup Thai tamarind concentrate, strained to remove grit
• 1cup tightly packed minced fresh herbs, any combination of
 at least two of the following: cilantro, flat-leaf parsley, tarragon, basil, mint
• 2limes, cut into wedges

1. Preheat the oven to 375°F. Grease two baking sheets.
2. Rinse the fish under cold water and pat dry thoroughly. Season them inside and out with salt and pepper and divide them between the baking sheets. Set aside in the refrigerator.
3. Heat a large skillet over medium-high heat. Add 3 tablespoons of the oil and sauté the onion for 10 minutes, until it starts to darken, then cook slowly over low heat for about 30 minutes, until it is dark brown and about half its original volume. Add the garlic, almonds, barberries, and tamarind, and cook over low heat until the mixture becomes fragrant, about 10 minutes. Stir in the herbs and season with salt and pepper. Let cool to room temperature.
4. Remove the fish from the refrigerator. Open each fish toward you, leaving the bottom flat against the pan. Spread the filling evenly from head to tail, then press the top half of the fish down firmly to cover the filling. Tuck any excess filling inside. Brush the fish with the remaining 2 tablespoons oil.
5. Bake for 12 to 15 minutes, until the top turns golden and the fish flakes easily. Serve with the lime wedges.

https://food52.com/recipes/41907-parvin-s-tamarind-stuffed-fish