French Bread Pizza

Name: French Bread Pizza
Ingredients: 8 ounces mild Italian sausage, casings removed; 1/2 medium red onion, halved and sliced 1/4 inch thick; 1 cup jarred pizza sauce; 3 cloves garlic, grated; 2 sprigs thyme, leaves only; 1 long loaf French bread or baguette (about 22 inches long), halved crosswise and cut horizontally; 2 cups shredded mozzarella; 1/2 green bell pepper, sliced into 1/4-inch-thick strips; 1/2 red bell pepper, sliced into 1/4-inch-thick strips; 2 tablespoons grated Parmesan; Crushed red pepper flakes and granulated garlic, for serving