Maple Cake 

1. Preheat the oven to 325F (165C). Grease and line the base of (2) 6 inch baking pans with circular parchment paper cutouts.
2. In a large mixing bowl, whisk together the flour, baking powder and salt. Set aside. In a small bowl or measuring cup, whisk the milk and vinegar to combine. Set aside. 
3. In the bowl of a stand mixer fitted with paddle attachment or in a large mixing bowl with a hand mixer, mix together the oil, sugar, and maple syrup at medium high speed to combine, about 1-2 minutes.
4. Beat the eggs one at a time into the wet batter followed by the vanilla extract.
5. Reduce mixer speed to low. In an alternating fashion, starting and ending with the dry ingredients, mix half of the dry ingredients into the wet batter followed by all of the milk mixture and ending with the remaining dry ingredients.
6. Stop the mixer. With a rubber spatula, scrape the sides and base of the mixing bowl to catch any unmixed ingredients.
7. Continue to mix the cake batter at medium speed for 1 minute to ensure that you have a smooth cake batter.
8. Equally divide the batter between the prepared baking pans and bake for 28-30 minutes or until a toothpick inserted into one of the cakes comes out clean.
9. Cool cakes in baking pans for 10-12 minutes before transferring to a cooling rack to cool completely to room temperature.

Maple Caramel Sauce

1. In a heat-safe mixing bowl or measuring cup, whisk together the heavy cream and maple syrup. Heat up the cream mixture in the microwave in 30 second intervals until hot but not boiled. Set aside until ready to use.
2. In a medium, deep bottom saucepan under medium heat, whisk together the sugar, water, and vinegar until all of the sugar is dissolved and the mixture starts to simmer, about 1-2 minutes.
3. Use a dampen pastry brush to wipe away any sugar granules from the sides of the pan, if present. 
4. Increase the heat to medium high and bring the sugar mixture to a boil without stirring. Continue to cook the syrup until it reaches a rich golden brown (amber) color, about 6-8 minutes. 
5. Remove the caramel from the heat. Carefully whisk the warmed heavy cream and maple syrup into the caramel. 
6. Whisk the butter into the hot caramel sauce followed by the salt and vanilla extract.
7. Pour the maple caramel sauce into a heat safe container and allow to cool completely before using. 

Maple Pecan Buttercream

1. In a small food processor or coffee grinder, ground the pecans into a flour. Take care to not over process the pecans to avoid ending up with pecan butter.
2. Use a fine mesh strainer, to sift the pecan flour into a small mixing bowl.
3. In a stand mixer fitted with paddle attachment or in a large mixing bowl with a hand mixer, cream the butter and salt (optional) at medium high speed until it is smooth and fluffy in appearance, about 2-3 minutes.
4. Reduce the mixer speed to low and mix in 2 cups of the confectioners’ sugar and all of the pecan flour into the creamed butter. Gradually increase the mixer speed back to medium.
5. Once all of the sugar and pecan flour have been incorporated into the butter, mix in the maple caramel sauce into the buttercream.
6. If buttercream appears to be too soft, mix in additional confectioners’ sugar 1/4 cup at a time until a thick but spreadable consistency is reached.
7. Increase mixer speed to medium high and mix the buttercream for an additional 30-60 seconds. The resulting buttercream should be smooth and fluffy in appearance.

Assembly

1. Level cooled maple cakes with a serrated knife or cake leveler. This will allow cakes to be evenly stacked and assembled.
2. Position the first cake layer faced up on a cake stand or serving plate of choice.
3. Spoon about a 2/3 cup of the buttercream onto the cake and spread into an even layer using an offset (angled) spatula.
4. Place the final cake layer faced down on top of the second layer. Using an offset spatula, apply a thin layer of the buttercream over the entire surface of the cake starting at the top and working down to the sides of the cake.
5. Smooth out the crumb coat using an offset spatula (top of cake) and bench scraper (sides of the cake).
6. Place the cake in the refrigerator for at least 30 minutes to allow the crumb coat to firm up before applying the final coat of buttercream.
7. Line the top border of the cake with the chopped pecans. Refrigerate the cake to set for at least 30 minutes before filling the inside of the pecan border with the maple pecan sauce. I recommend starting with 2 tablespoons and adding additional sauce 1/2 tablespoon at a time as needed.