Add almond flour, confectioners sugar, cardamom, cinnamon, and salt to the bowl of a food processor. Pulse 4 times for 3 seconds at a time. Scrape the bowl in between pulses.

Sift through a mesh strainer into a large bowl. Set aside.

In the bowl of an electric mixer fitted with the whisk attachment, whisk the egg whites and cream of tartar on medium speed until soft peaks are formed, about 2 minutes. (Reduce the speed to low if the egg whites are are ready before syrup.)

While the eggs are whipping, add the sugar and water to a saucepan. Cook over medium-high heat until a candy thermometer reaches 235°.

Pour the sugar syrup slowly into the running mixer (make sure it is on a very low speed).

Whisk until stiff peaks form, the meringue will be glossy and lukewarm, about 4 minutes, being careful to not overwhip. To check to make sure you are at the right stage, hold the bowl upside down, it should not slip in the bowl.

Move the almond mixture to the sides of the bowl, making a well in the center. Add the egg whites into the center. With a rubber spatula stir the egg whites from the center in a circular motion. The egg whites will pick up the dry ingredients, it takes about one minute to get it all incorporated. Fold in a J-shape 6-8 times.

Add to a large piping bag fitted with a large round tip (I use 1/2-inch). Pipe onto a Silpat or 2 baking sheets lined with parchment.

I hold the bag straight on top of where I am going to pipe and press until you reach the desired size. Release, lift, and move onto the next circle.

Drop the baking sheets onto the counter. Really give it a good slam. It will release the air bubbles and get rid of any little tails that might not have settled. (If you still have some, dip your finger in a teensy bit of water and gently press it down.) Sprinkle half of the shells with sea salt.

Bake in a preheated 200° oven for 15 minutes to dry out the shells. Increase the temperature to 350° and bake for another 9 minutes. The foot and edges should feel firm, and you can lift them off the parchment with a little effort.

Slice the paper or Silpat onto a wire rack and let cool completely, about an hour. Pipe salted caramel buttercream onto half of the shells. Top with remaining shells.

To store keep the macarons (filled or unfilled) in an airtight container in the refrigerator for up to three days. You can also freeze them for up to a month. Wrap carefully in groups of 6 and put them into a container so they don’t get crushed.