Summarize the following:
Save the remaining ¾ cup (150 grams) of brown sugar for later. Set the flour mixture aside when you are done. You will be adding this into your wet ingredients later on. Having all of the flours mixed in together first will give you more consistent muffins. Keep whisking until the oil and sugar are evenly combined. If you can't find any canola oil, you can use another flavorless cooking oil, such as vegetable oil. Stir the mixture well with a whisk after each egg that you add. Keep whisking until the yolks break, and there are no more streaks. Make sure that you are using plain, unsweetened applesauce. If you used the flavored kind, your apple muffins may turn out too sweet! Whisk in half of the flour mixture, then half of the buttermilk. Whisk in the rest of the flour mixture, and then the rest of the buttermilk. This will prevent things from clumping up too much. If you have not yet done so, peel, core, and cut the apple into ¼-inch (0.64-centimeter) chunks. Gently fold them into the batter using a rubber spatula. Be sure to scrape the bottom of the bowl often to ensure that the apple chunks mix in evenly. A quick and easy way to do this is with a large spoon or an ice cream scoop; this also ensures that each cup gets the same amount of batter. When you are done, gently tap the pan a few times against your counter. This will bring any air bubbles to the surface of the muffins. They are done when a toothpick poked into the center comes out clean. Let them cool on a wire rack for 15 minutes in the pan first. Then, run a butter knife around the muffins, and gently pull them out of the tin. Let the muffins finish cooling on the rack.
Preheat your oven to 400°F (205°C), and lightly grease a 12-hole muffin tin with cooking spray. Combine the pecans, 2 tablespoons (25 grams) of brown sugar, and cinnamon in a small bowl. Whisk together the flours, baking soda, and salt in a medium-sized bowl. Whisk together the oil and the rest of the brown sugar in a large bowl. Add the eggs one at a time into the oil mixture. Stir the applesauce and vanilla extract into the oil mixture with a whisk. Alternate between stirring in the flour mixture and the buttermilk mixture. Gently fold in the apple chunks. Fill each muffin cup ⅔ to ¾ of the way with batter. Sprinkle the pecan mixture from before on top of each muffin. Bake the muffins for 20 to 25 minutes. Let the muffins cool before serving them.