Food & Cooking Recipes Dessert & Treats Recipes Pie & Tarts Recipes Caramelized Onion Tart with Olives 3.7 (68) 3 Reviews By Martha Stewart Test Kitchen Martha Stewart Test Kitchen The recipes developed by our test kitchen team have undergone a rigorous process of development and testing, ensuring that every element is optimal, from ingredient amounts to method and cooking time. This process includes triple-testing recipes to ensure they meet our high standards. The many stellar cooks and food editors who have been part of our team include Sarah Carey, Lucinda Scala Quinn, Jennifer Aaronson, Shira Bocar, Anna Kovel, Greg Lofts, Riley Wofford, Lauren Tyrell, and Lindsay Leopold. Editorial Guidelines Updated on June 12, 2017 Print Rate It Share Share Tweet Pin Email Prep Time: 20 mins Total Time: 1 hr Servings: 4 Anchovies are the surprise ingredient, adding another layer of umami to this savory tart. Ingredients 1 tablespoon unsalted butter 2 tablespoons extra-virgin olive oil 2 medium onions, thinly sliced 2 tablespoons fresh thyme, leaves All-purpose flour, for dusting 1 sheet frozen puff pastry, thawed ¼ cup oil-cured small black olives, pitted and halved lengthwise 4 to 6 anchovy fillets (optional), rinsed Directions Preheat oven to 425 degrees. Melt butter with oil in a skillet over medium-high heat. Add onions and thyme, and cook until onions are golden and soft, about 10 minutes. On a lightly floured surface, roll out pastry, and trim to an 8 1/2-by-15-inch rectangle. Place on a parchment-lined baking sheet, transfer to oven, and immediately reduce oven to 400. Bake until pastry begins to rise, about 12 minutes. Arrange onions in a single layer over pastry, leaving a 1-inch border around edge. Top with olives and anchovies if using. Bake for 15 minutes. Reduce oven to 375 degrees, and bake until puffed and golden brown, about 15 minutes more (tent with foil if crust browns too quickly). Cut into squares. Rate it Print