Chicken Alfredo Pizza

Name: Chicken Alfredo Pizza
Ingredients: 2 pounds pizza dough ( homemade or storebought), fully risen, shaped into 2 balls; 1/2 cup Alfredo sauce ( homemade or storebought); 6 ounces ( 180 g ) uncooked boneless, skinless chicken breast; 1 teaspoon salt; 1 teaspoon black pepper; 2 tablespoons olive oil , divided; 2 cups ( 240 g ) grated mozzarella cheese; 1/2 cup ( 25 g ) grated parmesan cheese , plus more for serving; 4 tablespoons semolina flour or cornmeal; 1/2 medium red onion , thinly sliced into half-moons (optional); Chopped fresh parsley , for garnish