Preheat the oven to 350°F. Spray an 18x13x1 sheet tray with baking spray, and set aside.

In a medium-sized bowl, stir together the flour, baking soda, pumpkin pie spice, cinnamon, salt, and nutmeg, and set aside.

In a large bowl, whisk together the pumpkin puree, brown sugar, white sugar, oil, eggs, and vanilla until combined.

Add the dry ingredients to the wet and stir until combined and there are no dry patches.

Pour the cake batter into the prepared tray and smooth out the top.

Bake for 18-20 minutes until a toothpick inserted into the center comes out clean. Let it cool slightly while you make the frosting.

Place the butter in a small saucepot over medium-low heat and let it melt. Once melted, add the brown sugar and heavy cream, and whisk to combine.

Continue to whisk constantly until the mixture comes to a boil. Once it comes to a continuous boil, take off the heat and whisk in the powdered sugar a little at a time until fully mixed in.

Whisk in the bourbon and vanilla.

Add the pecans and salt, and stir to combine.

Immediately pour the frosting over the cake; it should go right to the edge, but if it looks like it may overflow, do not use it all; you do need to be careful while pouring, so do it slowly and evenly over the entire cake, don’t just dump it all on top (the pictured cake used all the frosting). Allow the frosting to set fully, about 1 hour. Slice and serve.