Preheat oven to 350 degrees. Spray 8-inch baking pan with Pam nonstick spray.
In a medium bowl, whisk together melted butter and brown sugar. Slowly add eggs and vanilla; whisk until smooth.
In a separate bowl, whisk flour, baking powder, and salt.
Gradually add egg mixture to flour mixture. Gently stir in pecans.
Spread into prepared baking pan.
Bake for 20-22 minutes, or until toothpick inserted in center comes out clean.
Cool on wire rack or serve warm.