Preheat oven to 350. Grease the bottom only of 13x9" pan and set aside.
In a bowl of an electric mixer, combine all ingredients except apples and pecans.
Beat on medium speed until batter is smooth, 2-3 minutes. Stir in apples and pecans by hand.
Pour batter into prepared pan. Bake at 350 degrees for 30-40 minutes or until toothpick inserted in center comes out clean; or until cake springs back when lightly touched with fingertip.
Cool completely on wire rack.
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In large saucepan, melt butter and add brown sugar.
Bring this mixture to a boil, stirring frequently.
Boil and stir for 1 minute until thickened. Remove from heat and add milk.
Beat with wire whisk until smooth. Add vanilla and beat again.
Then add enough powdered sugar until of desired spreading consistency; the frosting should be pourable.
Pour frosting over cake and spread to cover. Let cool and serve.
Makes approx 2 cups.