Preheat oven to 350 degrees. In a saucepan, heat the butter over medium heat until melted. Continue to cook for 3-4 minutes or until light brown and nutty smelling. Remove from heat and cool completely. Beat the cooled butter, granulated sugar, brown sugar, the eggs, and vanilla on medium speed until light and fluffy. Mix in dry ingredients until combined. Stir in the oats, butterscotch chips and chopped pecans. Spread evenly in an ungreased 10-inch cast iron skillet. Bake for 30-35 minutes or until golden brown around edges and on top. Do not overbake.