Prepare the pizza dough by rolling it out into a large rectangle, about 1/4 inch thick.
Caramelize the onions in a skillet with olive oil, salt, and sugar over medium heat for about 20-25 minutes until golden brown.
Mix shredded Gruyère cheese, cream cheese, and black pepper in a bowl, then fold in the cooled caramelized onions.
Spread the cheese and onion mixture over the rolled-out pizza dough, roll it into a log, and shape it into a wreath.
Make cuts every 1-2 inches along the outer edge of the wreath, brush with beaten egg, and sprinkle with seeds if desired.
Bake in a preheated oven at 375°F for 25-30 minutes until golden brown.