Preheat the oven to 350 degrees and grease a 9 x 13 inch pan with cooking spray or butter.

In a medium bowl, whisk together baking soda, salt, cinnamon, nutmeg, and flour. Set aside.

In the bowl of a stand mixer, beat together the butter and sugars until fluffy and lighter in color, about 4-5 minutes, scraping the bowl occasionally.

Beat in the eggs, one at a time, followed by the vanilla.

Add the flour mixture to the bowl, and beat on low speed until just combined. Stir in the apples and pecans.

Spread the batter over the pan evenly, then bake for 35 minutes. If the top is already browned, cover the dish with foil and bake another 10-12 minutes or until set.

When the cake is almost finished, make the caramel sauce. Combine the brown sugar, unsalted butter, and half and half in a saucepan over medium heat. Bring to a boil and continue to boil, whisking continuously for 2-3 minutes, or until slightly thickened.

Remove from heat and stir in the vanilla and salt, to taste.

While the cake and sauce are still warm, pour the caramel over top, spreading it to the edges.