Start by making the crust. Preheat the oven to 350F. In a large bowl, whisk together the water, 2 tablespoons of olive oil, and apple cider vinegar. Add the pizza dough mix and mix until the dough is completely hydrated. Note: You may need to add 1-2 tablespoons of water if your dough is crumbly.
Roll the dough out on a parchment lined baking sheet so that it is about 1/8 inch thick. Par-bake the crust for 15 minutes.
While the crust is cooking, caramelize the onions. Thinly slice the onion. Heat 1 tablespoon of olive oil in a large skillet over medium-low heat. Cook the onions slowly, stirring them every few minutes. After 10 minutes, sprinkle with a pinch of salt and continue to cook for another 5-10 minutes until onions have reduced in size and are caramel in color. Remove from heat.
Preheat your grill to 450. You can either use an outdoor grill or an electric grill. Brush walnut oil over both sides of the par-baked flatbread and grill on one side for 4-5 minutes. Flip the flatbread. Top it with an even layer of caramelized onions, figs, walnuts, and vegan cheese (if using). Cover the grill and cook for another 4-5 minutes. When the crust is cooked all the way through and the toppings are heated, removed from the grill.
Top with walnut oil, balsamic reduction, and fresh arugula. Serve immediately.