Mix the wet ingredients. In the bowl of a stand mixer, add the room temperature egg whites and whisk them at high speed using the whisk attachment. Then add the salt, cream of tartar, vanilla extract, and lemon extract.
Now add the sugar and food coloring. Once the egg whites begin to get foamy, slowly add the granulated sugar and yellow food coloring. Beat for another 4-5 minutes, or until stiff peaks form.
Sift the dry ingredients. In a separate bowl, sift the almond flour and powdered sugar and mix to combine. This is important for getting smooth macarons.
Fold in the egg whites. Add the egg whites to a large bowl and then 1/3 of the flour mixture. Fold the dry ingredients into the wet using a large rubber spatula. Once combined, add another 1/3 of the flour mixture, folding in again.
Fill the piping bag. Place a round piping tip into a pastry bag and fill it with batter. This can get messy so twist the bottom of the bag to keep it closed and avoid batter oozing out.
Pipe the lemon macarons. Pipe out 1-inch mounds of the batter onto the prepared baking sheets. Make sure to leave 1-2 inches in between each because they will continue to spread a little.
Get rid of air bubbles. Take the cookie sheets and bang them on the counter a few times to get rid of any air. I hit them pretty hard, about 10 times. Allow them to dry.
Bake. Preheat the oven to 300 degrees Fahrenheit. Make sure the oven is on the conventional setting, without the fan on. Bake one tray at a time for 16-18 minutes. Be careful NOT to underbake them or they will stick to the parchment paper.
Add the filling. Place a star piping tip (I used a Wilton 21) in a pastry bag, and fill it with lemon buttercream. Flip half of the macaron shells on their back and pipe a border around the edge. Then fill the empty center with your favorite lemon curd. Then place a macaron shell on top to complete the lemon macrons.