Line a 9×13-inch baking dish lengthwise with a long 13-inch wide piece of aluminum foil. Arrange a second 9-inch wide piece of foil perpendicular across first sheet, to create a sling. Push foil into corners, flush against the pan; coat with nonstick spray.

Whisk together ½ cup confectioners’ sugar and cornstarch in a bowl; set aside.

Pour ½ cup water into the bowl of stand mixer fitted with the whisk attachment. Sprinkle gelatin over water and let stand until gelatin is absorbed, about 15 minutes.

Meanwhile, combine remaining ¼ cup water and honey in medium saucepan. Carefully pour granulated sugar and salt into center of saucepan, avoid hitting sides of pan.

Bring mixture to a boil over medium-high heat (without stirring or agitating the mixture), and cook, gently swirling saucepan, until sugar has dissolved completely and mixture registers 242F°, 6–7 minutes.

Turn mixer speed to low and carefully pour hot syrup into gelatin mixture, try to avoid whisk and bowl.
Gradually increase speed to high and whip until mixture is very thick and coats the whisk, 10–11 minutes, scraping down bowl as needed.

Add vanilla, cardamom, and zest and mix until incorporated, 15 seconds, scraping down bowl as needed.
Quickly scrape mixture into prepared pan using greased rubber spatula then smooth top with a greased metal spatula.

Sift 2 tablespoons confectioners’ sugar mixture over marshmallow. Cover with plastic and let sit overnight at room temperature until firm.

Lightly dust a cutting board with 2 tablespoons confectioners’ sugar mixture and lightly coat a large knife with nonstick spray.

Turn marshmallow out onto cutting board and remove foil. Sift 2 more tablespoons confectioners’ sugar mixture over marshmallow then cut into 1-inch-wide strips. Cut each strip crosswise into 1-inch squares.

Working with 4–5 marshmallows at a time, toss marshmallows in bowl with remaining confectioners’ sugar mixture to coat, then transfer to a fine-mesh strainer and shake to remove excess powder.