Put half the olive oil in a medium skillet or saucepan and turn the heat to medium; a minute later, add the onion and cook, stirring occasionally, until softened, about 5 minutes; add the garlic and chile, stirring occasionally, for about 1 minute.
Turn off the heat and stir in the parsley, thyme, and bread crumbs, along with some salt and pepper to taste.
Layer half the lemon slices in the bottom of a small roasting pan.
Rub the fish with the remaining olive oil, sprinkle it with salt and pepper, and place it in the pan.
Put the onion mixture and remaining lemon slices on top of the fish.
Roast the fish until done, about 10 minutes for medium-rare (cut into it and take a look).
Drizzle with the lemon juice and a little more olive oil and serve hot or at room temperature.