In a small saucepan, bring honey, ¼ cup water, and rosemary leaves to a boil over medium heat. Remove from heat; cover and let steep for 20 minutes. Strain, and discard rosemary. Let cool completely.
In each of 4 Champagne flutes, combine ¼ cup grapefruit juice, 2 tablespoons rosemary-honey simple syrup, and ½ tablespoon Campari. Top each with ¼ cup Prosecco. Garnish with rosemary sprigs, if desired.
Recipe by Southern Lady Magazine at https://southernladymagazine.com/grapefruit-bellinis-recipe/