Grease a 9x13" baking pan and set it aside.

For the crust, in a medium bowl, mix graham cracker crumbs, chopped pecans, and brown sugar. Add melted butter and stir until combined. Press into the prepared pan. For a firmer crust, refrigerate or freeze until ready or bake for 10 minutes at 350°F (177°C).

For the caramel, melt the sugar in a saucepan over medium heat until it turns light amber. Carefully add in the butter and whipping cream, stirring until well combined. Whisk in the flour and salt, bringing it to a boil until thickened. Strain the caramel to remove lumps and cool slightly. Spread most of the caramel over the crust, reserving some for drizzling later.

For the whipped cream cheese layer, beat cream cheese, butter, powdered sugar, and vanilla together until smooth. In a separate bowl, whip cold heavy cream until stiff peaks form. Gently fold the whipped cream into the cream cheese mixture until combined. Spread this layer over the caramel layer and chill for at least 30 minutes.

For the apple pie filling, in a large bowl, toss diced apples with lemon juice. In a saucepan, combine flour, brown sugar, cinnamon, nutmeg, and water, bringing it to a simmer. Add apples and cook until softened, about 10 minutes. Let cool, then spread over the cream cheese layer.

For the whipped topping, whip heavy cream with powdered sugar and vanilla until stiff peaks form. Spread this over the apple pie filling, smoothing it out evenly.

Drizzle the remaining caramel over the top of the lasagna. Cover and chill for at least 2 hours before serving. This helps the layers set and makes serving easier.

Store leftovers in the refrigerator for up to 3 days.