1 cup unsalted butter; room temperature
1 cup light brown sugar; packed
2 cups all-purpose flour
1/4 teaspoon salt
1 tablespoon sugar
1 teaspoon ground cinnamon
Preheat oven to 325 degrees. Lightly butter 9-inch-diameter springform pan.
Using electric mixer, beat 1 cup butter in large bowl until light and fluffy. Add brown sugar and beat well. Using rubber spatula, mix flour and salt (do not overmix). Press dough into prepared pan. Combine 1 tablespoon sugar and cinnamon in small bowl. Sprinkle cinnamon sugar over dough. Cut into 12 wedges, using ruler as guide and cutting through dough. Pierce each wedge several times with toothpick.
Bake until shortbread is brown, firm at edges and slightly soft in center, about 1 hour. Cool shortbread completely in pan on rack. Remove pan sides. Recut cookies into wedges. (Can be prepared 2 days ahead. Store in airtight container at room temperature.)