Heat the olive oil in a large saucepan over medium heat. Add the onions; cook and stir until they turn soft and begin to turn golden brown, about 10 minutes. Stir in the brown sugar, and continue cooking and stirring until the onions are deep brown, about 10 minutes more. Pour in the balsamic vinegar, and simmer until the vinegar has reduced and become syrupy.
Meanwhile, place the bacon in a large, deep skillet, and cook over medium-high heat, turning occasionally, until crisp and evenly browned, about 10 minutes. Drain the bacon slices on a paper towel-lined plate then crumble and set aside.
Preheat an oven to 375 degrees F (190 degrees C).
To assemble the pizzas, spread each piece of lavash with 1/2 cup of pumpkin hummus and place onto a baking sheet. Sprinkle with about 1/4 cup of the caramelized onions. Top with some of the apple and crumbled bacon. Finally, sprinkle with 1/2 cup of fontina cheese.
Bake in the preheated oven until the pizza is hot and the cheese is bubbly and golden brown, about 10 minutes.