• Preheat the oven to 350 degrees F. In a large mixing bowl, stir together the flour, sugar, brown sugar, baking powder, baking soda, cinnamon, nutmeg, and salt.
• Add the oil, eggs, and vanilla and mix at medium speed for 1 to 2 minutes or until smooth.
• Stir in the apples and walnuts, if using, by hand. Spoon the batter into a greased and floured 13 × 9-inch cake pan.
• Bake for 38 to 45 minutes, or until the top springs back when lightly touched in the center. Cool on a wire rack.

Salted Caramel Sauce:

• In a saucepan, combine the brown sugar, cream, and butter. Cook, stirring constantly, over medium heat 5-7 minutes or until the brown sugar dissolves. Stir in the vanilla and salt.
• Poke small holes in the cake and drizzle 1/2 of the sauce over the cake to allow the caramel sauce to seep in. Let it seep in for about 5 minutes and then add the remaining caramel (if you want to drizzle caramel on top of the ice cream, keep some caramel on the side.
• Top with vanilla ice cream or fresh whipped cream and a drizzle of caramel.