Smoked Trout, Crème Fraîche & Pickled Onion Crostini

Name: Smoked Trout, Crème Fraîche & Pickled Onion Crostini
Yield: Makes 12 servings
Ingredients: ¼ cup thinly sliced red onions; ¼ cup red wine vinegar; 1 tablespoon sugar; ½ teaspoon kosher salt; 12 slices pumpernickel bread; 1 teaspoon lemon zest; ¼ teaspoon freshly ground black pepper; ½ cup crème fraîche; 12 ounces smoked trout; Chervil or dill