In a frying pan, melt butter with cinnamon, sweetener, vanilla. Add apples and toss in buttery mixture. Cook for about 5 minutes. Set Aside.
Cinnamon Crumble Topping
Add almond flour, Swerve, cinnamon, chopped walnuts together in separate bowl.
Add butter and mix with hands to make crumble. Set Aside.
Make Batter
Preheat oven to 350 on bake mode.
Put first five dry ingredients in a bowl. Set aside,
Add eggs to mixing bowl you are using for cake. Beat until frothy, about five minutes.
Add half of the dry ingredients mixture to eggs while mixer is on medium.
Add the entire apple mixture (made above)with all the melted butter.
Add remaining dry mixture. Pour into muffin liners.
Top with crumble (below).
Bake in muffin tins 25-30 minutes. You might get as many as 14 depending on the size of your cups. The inside muffin tests done when the temperature is 207 F.
How to Freeze
Muffins freeze well. Wrap each individually in plastic wrap. Take out to defrost about an hour in advance.
Notes
I used the Golden sweetener, which is a combination of erythritol and monk fruit. You can use granulated Swerve.