Remove the stems from the cherries. Reserve the juice from the jar of cherries. Note: These cherries are already seeded.
Add the cherries and 2 ounces of the juice* from the jar to a blender. Add the rosemary and zest. Puree on high speed until well blended, at least 2 minutes.
Pour the cherry mixture into an 8-inch square baking pan. Place in the freezer for 30 minutes; fully scrape up the cherry mixture with a fork then evenly spread back out in the pan. Every 30 minutes, repeat this freeze/scrape/spread step at least 4 more times until the mixture forms a scoopable sorbet.
Using an ice cream or cookie scoop or spoon, divide the sorbet among four sturdy cocktail or champagne glasses. Top each with the sparkling wine. Serve immediately along with small spoons for enjoying the sorbet or stirring it into the drink. Hint: If you stir it in, you’ll notice rosemary and zest “confetti” rises to the surface!