Heat 1 tbsp of olive oil in a skillet.
Add the onions and saute for about five minutes on medium-high heat. Add the salt and continue to saute until the onions begin to turn golden-brown, about 15-20 minutes.
Add the sugar, turn the heat down to medium, and continue to saute until the onions are deeply golden and very sweet. This should take about 20 more minutes. Turn off the heat and set aside.
Roll out the pizza dough, about 11 inches long and 8 inches wide. Sprinkle cornmeal on a cookie sheet and place the dough on it.
Spread the caramelized onions in a thin layer on top of the pizza dough, leaving a 1-inch border on all sides.
Sprinkle the garlic on top, and use the remaining oil to brush the edges of the tart.
Sprinkle on some salt and pepper to taste.
Bake in a preheated 500-degree oven for 11-12 minutes or until the sides are golden and the tart comes easily off the cookie sheet with a spatula.
Cut and serve hot.