Preheat oven to 350F and move rack to middle or lower middle position. Generously grease and flour a 9x13 baking pan. Set aside.
In the large bowl of a stand mixer, beat oil and eggs until fully combined. Add both sugars and vanilla and beat until mixture is smooth and creamy.
In a separate large bowl, whisk together the flour, salt, baking soda, cinnamon, and nutmeg.
Gradually add flour mixture to egg mixture and use rubber spatula to fold together just until incorporated. The batter will be thick.
Fold in the diced apples with spatula and spread batter into greased/floured pan.
Bake for 45 minutes or until toothpick inserted in center comes out clean. Don't over-bake. Cool cake completely on wire rack. Slice into squares to serve when cake is cooled.
For caramel drizzle: Melt caramels and 2 tsp water in saucepan, stirring constantly just until melted. Will be very hot! Drizzle with fork over cake squares. Sprinkle powdered sugar just before serving, if desired.