In a medium saucepan, combine the lemon juice, lemon zest, and sugar over medium heat. Stir until the sugar has dissolved, about 2-3 minutes.

In a separate bowl, whisk the eggs together, then gradually add them to the lemon mixture, stirring constantly to prevent curdling.

Cook over medium heat, stirring continuously for 5-7 minutes, until thickened and coats the back of a spoon.

Remove from heat and whisk in the butter until smooth. Allow to cool before using.

Preheat your oven to 375°F (190°C). Line two baking sheets with parchment paper.

In a bowl, sift together almond flour and confectioner’s sugar to remove any clumps. Set aside.

In a separate bowl, beat egg whites and cream of tartar until frothy. Gradually add granulated sugar, continuing to beat until stiff peaks form and the mixture is glossy.

Gently fold in the almond flour mixture, lemon zest, lemon juice, vanilla extract, and food gel until well combined.

Transfer the meringue mixture to a piping bag and pipe small rounds onto the prepared baking sheets.

Let them sit at room temperature for about 30 minutes to form a slight shell.

Bake in the preheated oven for 15-20 minutes, or until the macarons have risen and are firm to the touch. Allow to cool completely.