Prepare pan. Add parchment to bottom and spray including sides of pan.
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.
In a frying pan, melt butter with cinnamon, sweetener, vanilla. Add apples and toss in buttery mixture. Turn off stove. The apples will continue to cook inside the cake.
Add half of the dry ingredients mixture to eggs while mixer is on medium.
Add the entire apple mixture with all the melted butter.
Add remaining dry mixture. Pour into prepared pan and muffin liners.
Top with crumble (below).
Bake in an 8 or 9 inch cake pan 25-30 minutes. You will have batter left over to make 3 to 4 muffins. Bake muffins 20 minutes. Cake and muffins are done when the inside is at 207 degrees F.
Cinnamon Crumble Topping
Add almond flour, Swerve, cinnamon together in separate bowl.
Add butter and mix with hands to make crumble.
Glaze
Mix Confectioner's Sweetener with water (or heavy cream) adding a tablespoon at a time until you have a glaze thin enough to drizzle.
Flavor with maple extract. Add just 2 or 3 drops to glaze for a maple flavor.
Drizzle Glaze after cake has cooled OR You could just sprinkle with confectioner's sweetener.
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.