Caramelized Onions: heat the olive oil in a large skillet and add the onion. Cook for 10 minutes or until tender. Add the vinegar and sugar. Cook for 3 minutes or until sugar is dissolved and the mixture is light brown. Remove from the heat.
Place 3 tortillas on a baking sheet. Cover each tortilla with fontina cheese, caramelized onion and goat cheese. Top each with a second tortilla. Brush the tops with olive oil.
Bake at 350°F for 8-10 minutes or until the tops are golden brown and the cheese is melted. Repeat until all ingredients are used.