Put almond flour and powdered sugar in a bowl. Sift them through a fine sieve. This removes lumps. Fine texture helps make smooth macaron shells.

Place egg whites in a clean bowl. Add cream of tartar. Beat until foamy. Slowly add sugar while mixing. Beat until stiff peaks form. The mixture should look glossy.

Add yellow food coloring if you like. Gently fold in the almond flour mixture. Use a spatula. Fold slowly until the batter flows like thick ribbon.

Fill batter into a piping bag. Pipe small circles on parchment paper. Keep space between each one. Tap the tray gently to remove air bubbles.

Let the piped shells sit at room temperature. Rest for 30 to 40 minutes. A thin skin will form on top. This step is very important.

Preheat oven to 150°C (300°F). Bake for 15 to 18 minutes. The shells should not brown. Let them cool fully before removing from paper.

In a saucepan, mix lemon juice, zest, sugar,and egg yolks. Cook on low heat. Stir constantly until thick. Remove from heat and add butter. Let it cool.

Once lemon mixture is cool, fold in whipped cream gently. This makes the filling light and creamy like lemon pie.

Match similar shell sizes together. Pipe lemon filling on one shell. Place another shell on top. Press gently to sandwich them.

Place assembled macarons in fridge for 24 hours. This improves texture and flavor. Bring to room temperature before serving.