1. Sift almond flour and powdered sugar together three times into a large bowl.

2. Add 50g egg whites to dry ingredients and mix into a thick paste. Divide into 6 bowls (about 117g each).

3. Add gel food coloring to each bowl and mix until evenly colored.

4. In a small saucepan, combine 150g granulated sugar and 50ml water. Heat to 240°F (115°C).

5. While sugar syrup heats, whip 100g egg whites with cream of tartar on medium speed.

6. When syrup reaches 240°F, slowly pour into whipping egg whites. Increase to high speed and whip until stiff, glossy peaks form and bowl is cool (8-10 minutes).

7. Divide meringue equally among 6 colored bowls (about 42g each).

8. Fold meringue into each colored paste using macaronage technique: press batter against bowl, then fold. Repeat 30-50 times until batter flows like lava.

9. Transfer each colored batter to piping bags fitted with round tips.

10. Line baking sheets with silicone mats. Pipe 1.5-inch rounds holding bag perpendicular to sheet.

11. Firmly tap baking sheets on counter 5-10 times to release air bubbles.

12. Let piped macarons rest at room temperature for 30-60 minutes until they form a dry skin.

13. Preheat oven to 300°F (150°C). Bake one sheet at a time for 14-16 minutes.

14. Let cool on baking sheet for 5 minutes, then transfer to wire rack to cool completely.

15. Make buttercream: Beat softened butter until creamy. Gradually add powdered sugar, then vanilla and cream until fluffy.

16. Match shell pairs by size. Pipe buttercream onto flat side of one shell, sandwich with matching shell.

17. Store filled macarons in airtight container in refrigerator for 24-48 hours before serving for best texture and flavor.