Heat oil in a small saucepan over medium-high heat; stir in onion and balsamic vinegar. Reduce heat to medium-low, and cook for about 15 minutes or until onions are caramelized; let cool.
Sprinkle Cheddar and 1/2 cup Gorgonzola cheese evenly over prepared pizza dough; top evenly with onion mixture. Arrange apple over onion mixture; top with remaining Gorgonzola. sprinkle with walnuts.
Bake at 500° for 5 to 7 minutes or until browned and bubbly.