Generously butter the bottom and sides of an 11x7-inch glass baking dish and sprinkle with 1 tablespoon powdered sugar.
Add 1/2 cup cold water to the bowl of a stand mixer and add unflavored gelatin. Set aside to soften.
Combine remaining 1/2 cup water, sugar, corn syrup, cherry gelatin, and almond extract in a large saucepan over medium heat. Stir constantly until sugar and gelatin are dissolved. Heat the mixture to boiling, then reduce heat to medium-low. Cook, without stirring, until a candy thermometer immersed in the mixture reads 240 degrees F (115 degrees C), about 30 minutes. Watch carefully that syrup doesn't boil over; reduce heat if necessary.
Slowly pour syrup into the softened gelatin in the stand mixer bowl. Beat on low speed, then increase to medium-high and beat until marshmallow mixture has tripled in size. Pour into the prepared baking dish and smooth the top using a rubber spatula. Set marshmallow mixture aside and let stand, uncovered, 8 hours to overnight.
Dust a large cutting board with about 1 tablespoon powdered sugar. Loosen sides of marshmallow mixture from the baking dish, lift out onto the cutting board, and rub additional powdered sugar on top. Spray a sharp knife with cooking spray and cut marshmallows into 1-inch squares, 11 rows by 7 rows.
Toss marshmallows in a large bowl with remaining confectioners' sugar. Shake off excess sugar and transfer marshmallows to an airtight container.
