Preheat the oven to 450 degrees and put a pizza stone inside. (Alternatively, the pizza can be baked on a baking sheet.)
Caramelize Onions. Melt the butter in a large pan over medium heat. Add the onions and cook slowly, over medium heat, until they become tender and golden brown, about 30 minutes. Remove from heat and set aside.
Top and bake the pizza. Divide the pizza dough into four portions and place each on a piece of parchment paper. Gently stretch the dough out into a 12 inch circle. (The dough will be very sticky - sprinkle with a little flour if needed to keep your hands from sticking. Drizzle each round of dough with olive oil. Top each evenly with the caramelized onions, pear slices, and gorgonzola cheese. Bake until the edges of the pizza become golden brown, 8-12 minutes.
The caramelized onions can be made up to three days in advance and refrigerated.