For The Apple Filling:

1. Add the diced apple pieces to a large or medium saucepan and toss them in the lemon juice.
2. Whisk together the brown sugar, flour, and cinnamon in a small mixing bowl until combined. Sprinkle the mixture over the apples in the saucepan, and stir to combine. Add the maple syrup, and stir.
3. Place the saucepan over medium heat and cook the apples, stirring occasionally, for 15-20 minutes, or until the apple pieces are tender. Remove from heat and set aside to cool to room temperature.

For The Cinnamon Filling:

1. In a medium bowl, add the butter, brown sugar, cinnamon, and nutmeg and stir until the mixture resembles a thick paste. Set the filling aside.

For The Cinnamon Rolls:

1. Heat the milk in a microwave-safe bowl or measuring cup in the microwave for 60-90 seconds or until the temperature reaches 110-120°F. Whisk in the sugar until it has dissolved. Put the milk to the side.
2. Combine the flour, baking powder, baking soda, salt, and yeast in the bowl of a stand mixer, and whisk. Add the melted butter and egg.
3. Attach the bowl and a dough hook to the stand mixer and mix at low speed (2 on a KitchenAid) for 2 minutes. Pour the milk and sugar mixture into the stand mixer with a slow and steady stream.
4. Once all of the milk has been added, increase the speed of the mixer to medium (5 or 6 on a KitchenAid) and let it work the dough for 5 minutes or until the dough starts to pull away from the sides of the bowl and it springs back when poked.
5. Place the dough on a well-floured surface and knead gently for about 5 minutes or until the dough can be stretched thinly without tearing. Press the dough into a large rectangle with your hands, then use a floured rolling pin to roll the dough into a 12×18 rectangle that’s about ¼ inch thick.
6. Spread the cinnamon filling over the dough, leaving about 1 inch of one of the long sides of the dough without the filling so you can seal the cinnamon roll closed when you roll it. Spoon the apple pie filling over the dough evenly.
7. Use a pizza cutter or a large, straight-edge knife to slice the dough along the long edge into 12 equal strips about 1.5 inches wide each. Roll each strip and press the end into the roll to close it off. Alternatively, you can tightly roll up the long edge into one big log, then use a sharp knife or floss to cut the log into 12 equal rolls. Feel free to trim off the edges to make them a little bit straighter.
8. Place the rolls into a greased 9×13 baking pan or dish, cover the pan with plastic wrap, and store somewhere warm for 60-80 minutes or until the rolls have doubled in size.
9. Preheat the oven to 375°F. Remove the plastic wrap from the rolls, and bake for 22-25 minutes, or until the rolls are lightly browned on top and have filled the pan completely. Let the rolls rest for 10 minutes.

Brown Butter Cream Cheese Frosting:

1. In an 8 or 10-inch skillet over medium-high heat, melt the butter and let it cook until it stops sizzling and there are dark brown bits in the butter, about 2-3 minutes. Remove from heat, pour the butter into a medium or large heat-proof bowl, and let it cool to room temperature.
2. Add the cream cheese, vanilla extract, and salt, and mix at low speed until smooth. Then, beat in the browned butter until well combined. Gradually add the powdered sugar, 1 cup at a time, and mix until thick and smooth, and all of the powdered sugar has been added.
3. Spread the frosting over the cinnamon rolls while they are still warm, and serve them warm. To store in the fridge, allow the cinnamon rolls to cool completely before storing them in an airtight container in the refrigerator for up to 3 days.