1. Heat oven to 425 degrees F with rack in upper third. Coat a 9-inch square pan with cooking spray; set aside.
2. In a bowl, combine the brown sugar, 2 tbsp granulated sugar and cinnamon with 2 tbsp butter; set aside.
3. In a large bowl, whisk together the flour, 3 tbsp granulated sugar, baking powder, baking soda and salt. In another bowl, whisk together buttermilk, egg and 3 tbsp butter. Stir together the liquid and dry ingredients; dough will look rough. Knead on a floured surface until just smooth, about 5 turns.
4. Pat or roll dough into a 9-by- 13-inch rectangle. Brush with 2 tbsp butter. Spread dough with brown sugar filling, leaving 1/2-inch border. Use a spatula to lift dough from surface and roll, starting at a long side, to form a tight log. Pinch seam to seal log and slice evenly into 9 pieces. Place in prepared pan swirl-side up and press rolls down slightly. Brush tops with 1 tbsp butter.
5. Bake until edges are just golden brown and rolls are cooked through, 22 to 25 min. Loosen rolls from pan and invert onto a plate; reinvert to right side up onto a rack. Cool 5 min before icing.For icing::
6. In a bowl, beat together cream cheese and buttermilk until smooth. Beat in confectioners sugar to form icing; spread over rolls with a knife. Serve rolls warm. Makes 9 rolls.