In a small bowl, mix together the flour, hibiscus powder, baking powder, and baking soda; set aside. In large mixing bowl, use electric mixer to beat butter, sugar and salt
until light and fluffy.
Add egg, lemon juice, lemon zest and lemon extract; beat until well combined; remove beaters. Using heavy-duty wooden spoon, add flour mixture and mix until just combined (it will seem too dry, at first, but will be soft and sticky when combined.)
Cover and refrigerate for at least 1 1/2 hours. When ready to bake, line 2 cookie sheets or sheet pans with parchment paper; preheat oven to 350*F.
Working one at a time, form dough into 1" ball and roll into sparkling sugar. Place on lined baking sheet; press down lightly. Repeat with remaining dough, spacing cookies one inch apart.
Bake at 350F for approximately 10 minutes for softer cookie to 12-13 minutes for crisper cookie.
Cool on baking sheets on wire racks for a few minutes; serve or store in airtight container.
The hibiscus powder is red, but the cookies will be a nice lavender color. You could roll them in the sparkling sugar and then use a cookie stamp.