Baked Challah French Toast

Name: Baked Challah French Toast
Prep time: 20 min
Cook time: 30 min
Total time: 50 min
Cuisine: American
Ingredients: butter for greasing; 1.5 loaves challah, cut into 1-inch pieces; 0.75 cup white sugar, divided; 1 tablespoon ground cinnamon, or more to taste; 3 cups milk; 8 large eggs; 1 tablespoon vanilla extract; 1 teaspoon salt; 1 stick unsalted butter, cut into 10 pieces