For the puttanesca sauce: Heat the oil in a medium saute pan over medium-high heat until hot. Saute the onions and garlic until translucent, about 2 minutes, and then stir in the olives, capers and anchovies, tossing to combine. Add more oil, if needed. Stir in the tomatoes and bring to a boil. Once at a boil, stir in the tomato paste, followed by the oregano and red pepper flakes. Taste and adjust the seasoning.
Preheat the grill to medium-high heat.
Sprinkle the fish with salt and black pepper and squeeze with 1 piece of the lemon. Grill the fish seasoned-side down without moving it, 4 to 5 minutes, and then sprinkle salt, black pepper and lemon juice on the other side of the fish and flip. Continue grilling, another 4 to 5 minutes.
Top the fish with the Puttanesca Sauce.
This recipe was provided by a chef, restaurant or culinary professional and may have been scaled down from a bulk recipe. The Food Network Kitchens chefs have not tested this recipe, in the proportions indicated, and therefore, we cannot make any representation as to the results.