Make the Pumpkin Cake

1. Preheat the oven to 350°F. Evenly spray the bottom and sides of three 8-inch round baking pans with baking spray with flour. Set aside.
2. In a medium-size bowl, whisk together the flour, baking powder, baking soda, cinnamon, allspice, salt, and nutmeg. Set aside.
3. In a large bowl or the bowl of a stand mixer fitted with the paddle attachment, beat the eggs at medium-high speed while gradually adding the granulated sugar and brown sugar until the mixture is lighter in color, 3 to 4 minutes.
4. Mix in the pumpkin, sour cream, and vanilla until just combined.
5. Slowly add in the flour mixture, alternating with oil, while mixing on low. Begin and end with the flour mixture and mix until just combined.
6. Divide the batter equally between the prepared pans. Bake for 28 to 33 minutes, or until a toothpick inserted in the center comes out dry with a few crumbs.
7. Leave the cakes in the pan to rest for 10 minutes before removing them onto a wire rack to cool to room temperature.

Make the Maple Pecan Frosting

1. Preheat the oven to 275°F.
2. Evenly place the chopped pecans onto a baking sheet lined with parchment paper. Bake for 5 to 7 minutes. Transfer the pecans to another baking pan to quickly cool.
3. Once cooled, place the pecans into a food processor and pulverize them to an almost powdered state.
4. In a bowl of a stand mixer fitted with the paddle attachment, beat the butter until smooth.
5. Reduce speed to low, slowly add in 4 cups of powdered sugar, ½ cup of pulverized pecans, and 1 tablespoon of maple syrup.
6. Add the remaining ½ cup of pecans, remaining maple syrup, and remaining 2 cups of powdered sugar (1 cup at a time). Continue to mix until the frosting becomes smooth and spreadable.

Make the Maple Caramel Sauce

1. In a heavy-bottomed saucepan, combine the maple syrup, butter, heavy cream, and salt.
2. Bring the mixture to a boil over medium heat, stirring constantly.
3. Attach a candy thermometer to the pan but touching the bottom of the pan.
4. Boil the caramel without stirring until mixture reaches 225°F. Remove it from the heat and gently stir in the vanilla. Allow it to cool.

Assemble the Cake

1. Add ½ cup of the Maple Pecan Frosting to a piping bag fitted with a round tip and set aside.
2. Spread about ⅓ cup of the frosting on top of the bottom cake layer.
3. Using the filled pastry bag, pipe a circle at the edge to create a dam on the frosting.
4. Spread the Maple Caramel Sauce within the piped barrier.
5. Place a second cake layer on top and repeat Steps 3 and 4.
6. Place the third cake layer on top and frost the top and sides of the cake.
7. Spread any remaining caramel on the top with toasted pecans.
8. Allow the caramel to drizzle, then pipe a few swirl decorations on top.