Macaroni and cheese from scratch

1/2 teaspoon salt 1/4 teaspoon freshly ground black pepper 1 (10-oz.) block extra sharp Cheddar cheese, shredded $ 1/4 teaspoon ground red pepper (optional) 1/2 (16-oz.) package elbow macaroni, cooked Preparation 1. WHISK FLOUR INTO BUTTER Preheat oven to 400°. Microwave milk at HIGH for 1 1/2 minutes. Melt butter in a large skillet or Dutch oven over medium-low heat; whisk in flour until smooth. Cook, whisking constantly, 1 minute. 2. WHISK IN WARM MILK Gradually whisk in warm milk, and cook, whisking constantly, 5 minutes or until thickened. 3. WHISK IN CHEESE Whisk in salt, black pepper, 1 cup shredded cheese, and, if desired, red pepper until smooth; stir in pasta. Spoon pasta mixture into a lightly greased 2-qt. baking dish; top with remaining cheese. Bake at 400° for 20 minutes or until golden and bubbly.