Spray an 8-inch-square baking pan with cooking spray; line with parchment, leaving an overhang on all sides. Spray parchment; dust with confectioners' sugar. Place 2/3 cup cold water in a mixer bowl; sprinklegelatin over it, and let soften, about 5 minutes.Advertisement
Bring granulated sugar and 1/2 cup water to a boil in a pan, stirring often until sugar dissolves. Wash sides of pan with a wet pastry brush to keep sugar crystals from forming. Boil, without stirring, until temperaturereaches the soft-ball stage (238 degrees) on a candy thermometer. Remove syrup from heat; add to softened gelatin. Using the mixer's whisk attachment, hand-stir about 30 seconds to cool. Place bowl on mixer stand. Whisk on medium-high until soft peaks form and mixture holds its shape, about 8 minutes. Whisk in food coloring and lemon extract.
Transfer mixture to pan, and quickly smooth top. Let stand until set, at least 3 hours and up to 3 days. Cover tightly if storing for longer than a few hours.
Shortly before serving, lift parchment edges to remove cooled marshmallow block from pan. Using a warm knife, cut into 1-inch squares.