Position the lower third of the oven rack. This is located right below the oven's center. Place 4 additional baking sheets with silicone macaron mats on top of the rack, along with an empty baking sheet. the oven to 300 degrees Fahrenheit.

Sift the almond flour, confectioners' sugar, and strawberry powder into a big basin using a fine-mesh sieve. Repeat 2-4 times, then throw any clumps away. The clumps shouldn't be forced through the sieve!

The egg whites and cream of tartar should be whipped on medium speed in the bowl of a stand mixer with the whisk attachment until frothy. Granulated sugar should be added gradually. Whip until soft peaks develop while increasing the speed to a high level. If used, add 1-2 drops of food coloring.

Whip constantly at high speed until a beautiful, thick meringue forms. Take particular caution not to whip too much.

Fold half of the almond mixture into the meringue with a silicone spatula until completely incorporated. At this point, it's acceptable to be a little rough. You want to remove some of the batter's air.

Gently fold in the remaining almond mixture after adding it. The batter might go awry at this stage. Problems with the macarons' baking will result from either overmixing or undermixing. You'll need to pause after a few stirs to assess the batter's consistency. Do this repeatedly until the batter is perfect. (The batter ought should flow like lava and be glossy. As you draw a figure 8, you can let the batter flow off the spatula without worrying about it breaking. You should be able to rest the figure 8 you just created on top of the batter in the bowl without it sinking in or bending.)

Transfer the batter to a large pastry bag fitted with a medium round piping tip. Be as gentle as you can with the process. Try not to overwork the batter.

Pipe 1 to 2-inch rounds onto the prepared baking sheets. Gently tap the baking sheet on the countertop to bring any air bubbles to the surface. Let the macarons sit for 30 to 60 minutes, until a dry skin forms on the surface. They should not feel sticky to the touch when going into the oven.

Bake for 15 to 18 minutes, one sheet at a time. When you can gently press on the macaron's shell and move your finger back and forth without it shifting, the macarons are finished. The macaron needs one or two more minutes to bake if the top is wavy.

On the baking sheet placed on a wire rack, the shells can cool fully. Wait until the shells have totally cooled before attempting to take them off the silicone pad; otherwise, they might stick and shatter.

Strawberry buttercream is sandwiched between two cookies. Bring the filled macarons to room temperature right before serving and store them in the refrigerator for at least one to three days. This is how they taste best.

Combine the sugar, egg whites, and salt in the bowl of a stand mixer. Set the bowl over a saucepan filled with 1 inch of barely simmering water. Whisk gently and continuously while heating the mixture. It should register 150°F on an instant-read thermometer. The sugar should be fully dissolved.

Transfer the bowl to the stand mixer and fit it with the whisk attachment. Beat on medium speed until the mixture is the consistency of shaving cream and cooled slightly, 1-2 minutes. (If the meringue is warm it will melt the butter.)

Add the butter gradually, 1 tablespoon at a time, until the mixture is creamy and smooth. (Only add the subsequent tablespoon of butter after the previous one has been thoroughly incorporated.)

After all the butter has been added, scrape the bowl's sides, then beat on medium-high for about 30 seconds, or until the mixture is light and fluffy.

Strawberry powder should be added and mixed on medium-high until fully blended.