Position a rack in the center of the oven and heat the oven to 425°f. Line a large rimmed baking sheet with foil.
Cook the bacon in a 12-inch skillet over medium heat until crisp, 10 to 12 minutes. Using a slotted spoon, transfer the bacon to a paper-towel-lined plate.
Pour off all but 2 Tbs. of the bacon fat from the skillet. Add the onion to the skillet, and cook over medium heat, stirring occasionally, until starting to soften, about 3 minutes. Add the tomatoes, vinegar, and sugar, and cook, stirring occasionally, until the tomatoes break down, about 10 minutes. Stir in the cooked bacon.
Meanwhile, whisk the mustard and lemon juice in a small bowl. Pat the fish dry with paper towels and arrange on the prepared baking sheet. Brush with the mustard-lemon mixture, and season lightly with salt and pepper. Bake the fish until just opaque in the center, 10 to 12 minutes. Spoon some of the tomato-bacon jam onto each plate, top with the fish, and serve.
nutrition information (per serving):
260, Fat Calories
10, Saturated Fat
3.5, Polyunsaturated Fat
1.5, Monounsaturated Fat
Photo: Scott Phillips