How to Make It
Preheat oven to 200° with racks in upper and lower third. Cut 12 pieces of parchment paper, each 4 in. square, and set aside.
In a deep bowl with a mixer on high speed, whip egg whites and cream of tartar using whisk attachment until thick and foamy. While beating, slowly add a few tbsp. sugar every 30 seconds or so, then whip until meringue holds very stiff peaks, about 4 minutes total. Beat in vanilla.
Spoon meringue into a pastry bag fitted with a #127 petal piping tip,* or spoon into a gal.-size heavy resealable plastic bag, then cut off 1 corner to make a 1/2-in.-wide opening. (Meringue will be sticky; you may need a second spoon to help scrape it off the first.) Place a dab of meringue in center of a cake turntable and top with a parchment square. Or, if you don’t have a turntable, dab meringue on center of a small plate, then add parchment.
To form flower, start at center of parchment. With pastry bag perpendicular to parchment, pipe with even pressure to form a 2-in.-long meringue strip for first petal. Release pressure on bag and lift tip to form a small peak at end of petal. Rotate turntable or plate slightly, return pastry tip to center of turntable or plate, and form another petal. Continue until you have a complete flower with 12 to 15 petals. Gently set parchment with meringue on a rimmed baking pan. Repeat with remaining parchment squares and meringue, filling a second pan as needed.
Bake meringues until firm to the touch and no longer sticky, but not yet beginning to brown, 1 to 1 1/2 hours; switch pan positions halfway through baking. Turn off heat and leave meringues in closed oven to cool and crisp at least 8 hours and up to 2 days.
For yellow flower centers, using end of a toothpick, add 1 large smear of yellow food coloring and 1/16 tsp. white food coloring to 1 tsp. water; mix well. With a small paintbrush or cotton swab, gently paint a yellow circle in center of each meringue flower.
Make ahead: Up to 2 days, airtight at room temperature or in oven (unless weather is humid; then use as soon as possible).
* Find piping tip, gel paste food coloring, and pearl dust at Michael’s stores and on amazon.com.