Sift almond flour and powdered sugar into a medium mixing bowl. Set aside.
In the bowl of an electric mixer with the whisk attachment, beat the egg whites on medium until foamy. Add the cream of tartar and continue to beat. While beating, add about 1 tablespoon sugar at a time. Increase speed to medium-high and mix until stiff peaks. You should be able to turn the bowl upside down without it sliding. Add the lemon juice and gel food coloring and beat on medium until combined.
Add the almond flour and powdered sugar by sifting it into the meringue (this is the second time sifting). Use a rubber scraper and gently fold the ingredients together by scraping the sides clockwise, starting at the bottom and then cutting down through the middle once you get to the top. The batter will thin up as you mix. Test the batter by dropping some back into the bowl. It will fall off the spatula like thick lava and the edges of the dropped batter will dissolve within ten seconds.
Place batter in a piping bag fitted with a Wilton A1 piping tip.
Pipe out 1.5 inch rounds 2 inches apart on 3 baking sheets covered with parchment paper. (I recommend using templates under the parchment paper and pulling them out after piping.)
Slam the baking sheets firmly on the counter a few times to get the air bubble out so that they don't crack the macarons while baking.
Let the batter dry 20-30 minutes or longer until you can lightly touch it without it sticking to your finger.
Preheat the oven to 300 degrees Fahrenheit and bake for 18-20 minutes. Place pan on a cooling rack for 15 minutes and then slide the parchment onto the cooling rack and let the macarons cool completely.