Preparation

• Electric mixer method:
  In a large mixing bowl, sprinkle yeast over water with the sugar. Let proof and soften for about 5 minutes. With paddle attachment, add oil, and stir to blend. Add 1 cup flour and stir until smooth. With dough hook attachment, add remaining 3/4 cup flour and salt and knead until silky smooth and elastic, about 5 minutes.
  Food processor method:
  Place flour and salt in food processor bowl; process briefly just to blend. Combine oil and yeast mixture, pour down feed tube and process just until mixture is a lumpy mass. Place the mixture on a lightly floured work surface and knead sticky dough for about 5 minutes until satiny and smooth. Knead in no more than three tablespoons additional flour.
  
  Place dough in large bowl, cover and let rise in a warm place away from drafts until doubled in bulk, about 1 hour.
  While dough is rising, prepare the filling.
  Heat the oil and butter in a large skillet and over medium-low heat saute the onions, garlic and salt until soft and transparent, about 10 to 15 minutes.
  Stir occasionally to prevent onions from browning or scorching. Add the water and thyme, and over high heat cook until the water evaporates. Over low heat, continue sauteing about 20 minutes longer, until onion mixture is very soft and translucent. Transfer to a sieve to drain any excess liquid. (yield at this time is 3 cups). Remove sprig of thyme. Set aside to cool.
  Adjust the rack in the lower third of the oven and preheat the oven to 425 degrees. Rub 1 tablespoon olive oil over the bottom of a 10 x 15 jelly roll pan or a 12-inch pizza pan.
  Punch dough down. With fingertips, press and stretch the dough to fit the pan. If the dough becomes elastic, rest a couple of minutes, then press again. Cover dough loosely with plastic wrap and let rest about 30 minutes or until puffy.
  Spread onion filling evenly over risen dough. Place anchovies decoratively over top of tart. Bake for 12 minutes. Rotate pan, and bake until crust is cooked through and golden, about 12 minutes more.
  Remove from oven, and using a spatula, transfer tart to a wire rack. Arrange olives decoratively on tart.
  Serve warm or room temperature. Cut rectangles, squares or wedges while warm or at room temperature.
  For an extra crisp crust, spread filling over dough, and rather than allow time for the dough to rise and become puffy, bake it right away.
  For a more bread-like crust, let dough rise in baking pan until puffy, then spread filling on top and bake.
  Note: If anchovy fillets taste too salty, rinse them in cold water and dry thoroughly with paper towels.