3/4 cup egg whites (8-9 eggs)
1 1/2 cups granulated sugar
1 1/2 pounds almond paste
1/8 cup Meyer lemon juice
Powdered sugar (optional)
Put egg whites and sugar in top of a double boiler or bowl set over a pot of simmering water. Whisk occasionally, until sugar dissolves and mixture is hot but not boiling, about 15 minutes.
Transfer mixture to a mixing bowl. Beat at medium speed with an electric mixer for 5 minutes, then at high speed for 2 more minutes. On low speed, add the almond paste in tablespoon-size chunks until completely incorporated (about 10 more minutes). Add lemon juice to taste.
Transfer mixture to a pastry bag.
Pipe 3 inch circles onto baking sheets lined with parchment paper.
Let dry at least 24 hours, uncovered at a cool temperature or in the refrigerator.
When ready to bake, preheat the oven to 325°. Remove the macaroons from baking sheet and shower them with powder sugar . Return the cookies to the baking sheet. With your thumb and forefinger, gently squeeze the perimeter of each macaroon to break the dry skin in a few places so the cookie can expand while baking. Bake 20-25 minutes, or until the edges are golden.
Remove to a rack and let cool.