Recipe adapted from Martha Stewart.
Preheat oven to 350°. Spray a 12-cup Bundt pan with cooking spray. Set aside.
Sift together flour, cinnamon, baking soda, and salt. Set aside.
Using an electric mixer on high speed, combine oil, sugar, and eggs on high speed until blended. Mixture will be lemon yellow. Decrease mixer speed to medium, and gradually add flour mixture. Mix just until blended. Mix in vanilla. Stir in apples and nuts.
Pour batter into prepared pan. Bake 75-90 minutes, or until a wooden pick inserted in the center comes out clean.
Remove cake from oven and cool slightly on wire rack. Then, invert cake onto rack to cool completely.
Combine all ingredients in a small saucepan. Cook over medium heat, stirring constantly until thickened to desired consistency.
Pour over cake immediately.