Preheat oven to 350° F. Butter a 9" x 13" pan. In a small saucepan, heat butter just until melted. Pour melted butter over sugar. In a separate bowl, mix dry ingredients together: flour, baking powder and salt. Whisk eggs and vanilla into butter/sugar mixture, and then add in the dry ingredients. Pour into a 9" x 13" pan and sprinkle with one teaspoon salt. Bake for 25 to 35 minutes, just until set. Cut and serve when cool.