Over a large bowl, sift together almond flour and powdered sugar. Add 2 egg whites and mix to form a paste. Set aside.
Using a hand mixer or stand mixer, whip 2 egg whites on medium speed to soft peaks.
In the meantime, in a small saucepan, cook 200g of sugar and 50g of water on medium heat until the syrup reaches 245 degrees F.
Once the egg whites are forming soft peaks, slowly pour in the syrup with the motor running on medium speed. Then crank up to high speed and mix until the meringue turns super white and glossy, about 4 minutes. Add yellow food coloring and mix to combine.
Spoon a quarter of the meringue over the almond paste mixture and stir to combine. Don’t worry about deflating any egg whites here. You are only loosening up the paste so it’s easier to mix with the rest of the meringue. Once the mixture is uniform, add the rest of your meringue and fold until combined.
Spoon macaron batter into a piping bag fitted with a plain round tip, about ¾” wide. Pipe your macarons in perfect little circles on parchment-lined baking sheets. Once piped, tap your baking sheet on your counter a couple of times to get rid of any air bubbles.
Bake for 15 minutes. The macarons should come off the parchment paper easily. Let them cool on the baking sheet. When cool, pipe the details with royal icing on half of the shells.
To assemble, spoon or pipe 1 tsp of lemon curd between 2 macaron shells. Refrigerate overnight before serving.