This is another of those gorgeous Greek braised dishes, full of olive oil. Please don't stint, it makes all the difference.
1/2 cup extra virgin olive oil, plus more for drizzling
1 oz butter
Juice of 1 lemon
2 medium onions, finely sliced
coarse salt and freshly ground pepper
1/4 tsp Aleppo pepper
8 cloves garlic, minced
1 teaspoon dried Greek oregano
1 glass white wine
1 cup of chicken stock (or more wine)
4 tomatoes, each cut into 8 pieces
6 medium red potatoes, peeled, thinly sliced and boiled for 2 mins then drained into a colander
4 large skinless haddock fillets
Preheat the oven to 200oC. Heat the olive oil in a medium saucepan over medium-low heat. Add the butter and when it begins to foam, add the onions along with a pinch of salt, stirring to coat well. Cook for 8 to 10 minutes. Raise the heat to medium and cook for 4 to 6 minutes longer, or until the onions are golden brown. Season with salt and pepper to taste. Add the garlic and saute for 1 minute. Add the oregano and stir to combine. Add the wine & lemon juice and bring to a boil. Boil for about 5 minutes, or until the pan is almost dry.
Stir in the tomatoes, the stock, and a pinch of salt. Return to a boil, then lower the heat to a simmer, cook for about 10 minutes, season and remove from the heat and set aside.
Heat a large frying pan to medium-high. When hot, add 2 tablespoons of olive oil. Sear the fish for 1 min each side, only one or 2 at a time. Don't crowd the pan. Drain them on kitchen towel.
Mix the potatoes with about 2/3 of the sauce and spread it into a lasagne dish. Put the fillets on top and pour the remaining sauce over the whole thing. Bake for about 12 minutes, or until the fish is opaque and cooked through.