Preheat oven to 350 degrees.
Coat a Bundt pan with Baker's Joy spray, or lightly grease and flour pan.
Spread walnut pieces on a cookie sheet or shallow ovenproof pan. Toast walnuts in oven, stirring occasionally to brown evenly, about 10 minutes, until lightly browned. Set aside.
In a bowl, sift together flour, baking soda, salt, cinnamon and nutmeg; set aside.
In a large nonreactive bowl, combine lemon juice and 3 or 4 cups cold water. Peel apples and cut into 1/2-inch dice, then put in lemon-water solution to prevent browning. Set aside.
In a mixing bowl, cream together sugar and oil with an electric mixer. Add eggs one at a time, beating well after each addition.
Add vanilla, then add flour mixture, and mix until it is mostly incorporated. When batter begins to get stiff, remove whip or beaters and finish mixing with a rubber spatula. Drain apples well and fold into the batter along with the walnuts.
Pour batter into prepared Bundt pan and bake about 45 minutes until a toothpick or knife blade inserted near the center comes out clean. Remove cake from oven and let cool in the pan for 10 to 15 minutes before inverting onto a platter.
With a paring knife, cut deep slits all over the cake. Ladle Caramel Sauce generously over the cake so that it soaks into the slits and glazes the outside.
Serve cake warm with additional Caramel Sauce and, if desired, whipped cream.
Cake keeps well at room temperature.