Heat oven to 350F. Melt butter in a 2-quart saucepan over medium heat (2 to 3 minutes). Add brown sugar; mix well. Cool 5 minutes. Stir in eggs and vanilla. Add flour and salt; mix well. Stir in pecans.
Spread batter into a lightly greased 13x9 inch baking pan. Bake for 22 to 27 minutes or until set. Cool completely, sprinkle with powdered sugar.