1. Heat oven to 350°F. Grease 12-inch round pizza pan. If using a disposable pan, place on baking sheet to bake.
2. Beat melted butter, sugar and vanilla with spoon in large bowl. Beat in eggs. Stir in dry ingredients; beat with spoon until well blended. Spread in pan.
3. Bake 20 to 22 minutes or until top springs back when touched lightly in center. Cool completely. Add yellow and red food color to frosting for desired shade of orange. Frost brownie; garnish to resemble a jack-o-lantern. 12 to 16 servings.