Preheat the oven to 150 degrees F (65 degrees C).
Spread the lemon and orange zest
on a baking sheet lined with parchment paper. Let dry in the oven, about 1 hour. Using a spice grinder
, reduce the zest to a fine powder. Set aside.
Mix the port
, orange liqueur
and peaches in a big mason jar. Keep in the refrigerator until ready to serve.
Rim tall serving glasses with the zest powder. Pour the sangria into the glasses, filling them one-third of the way full. Add the frozen grapes and top with the sparkling wine