Line a cookie sheet with a silicone mat or parchment paper. Set aside.
Using a food processer pulse the powdered sugar and almond flour until fully combined and rid of lumps. Don’t do this for too long or you will make almond butter. Sift the dry ingredients into a large bowl. If you don’t have a food processor you can sift the ingredients together.
In a medium bowl, prepare the french meringue. Beat the egg whites on low speed until they get frothy. Increase the speed and slowly add the sugar. If you add the sugar too fast you will deflate the meringue. Beat until stiff peaks form.
Add the french meringue into the dry ingredients and begin to gently fold with a silicone spatula. You will know the batter is ready when the ingredients are fully combined and not streaky. You should be able to hold the spatula above the bowl and draw a figure 8 smoothly without the batter breaking off. A good way to test if the batter is ready is to place a very small amount in your piping bag and pipe it onto your mat. If the batter is stiff and does not spread at all, then it is not ready. If the batter immediately runs out, then you have over folded. The batter should spread slightly and the tops should even out (there shouldn’t be any little tips sticking out), but it should not be runny.
Transfer the batter to a piping bag with a piping tip. Pipe 1-inch disks onto the prepared cookie sheet.
Firmly tap the cookie sheet onto the counter 3 or 4 times to bring any air bubbles to the surface. Use a toothpick to pop any remaining air bubbles.
In a small bowl combine the ground cinnamon and granulated sugar. Sprinkle the mixture over the wet macarons.
Let the macarons rest for an hour.
Preheat the oven to 280 degrees (F). This is the temperature that I have found works well for my oven, but you may need to play around with the temperature to find what works best for your oven.
Place the macarons on the middle rack of the oven and bake for 5 minutes, rotate the cookie sheet, bake for another 5 minutes and rotate the cookie sheet again, bake for 5 minutes. 15 minutes in total. The macarons should not have any color to them, and they should peel off of the mat easily.
Remove from the oven and allow to cool completely.
If the macarons were baked correctly they should easily peel off of the silicone mat.
In a medium bowl with a hand mixer, beat the butter until it is very soft and creamy. The butter needs to be really soft or your buttercream won’t be as fluffy as it should be.
Add half of the powdered sugar. Beat until fully combined.
Add the rest of the powdered sugar and the vanilla extract. Beat on medium speed for 5-6 minutes.
Add the heavy cream. If the buttercream is too thick add more, 1 tablespoon at a time until it reaches the desired consistency.
Snickerdoodle Macaron Assembly
Transfer the buttercream frosting to a piping bag fitted with a piping tip.
Pipe your desired amount of icing onto the inside of one macaron shell.