Place a rack in the center of the oven and pre-heat the oven to 350 F. lightly mist an 8-inch square baking pan with vegetable oil spray and set the pan aside.
Place the cake mix, lemon gelatin, orange juice, oil and eggs in a large mixing bowl and beat with an electric mixer on low speed until the ingredients are just incorporated, 30 seconds.
Stop the machine and scrape down the side of the bowl with a rubber spatula. Increase the mixer speed to medium and beat the batter until smooth, 1 ½ to 2 minutes longer, scraping down the side of the bowl again if needed.
Pour the batter into the prepared pan, smoothing the top with the rubber spatula, and place the pan in the oven.
Bake the cake until it is golden brown and the top springs back when lightly pressed with a finger, 45 to 50 minutes. Transfer the pan to a wire rack
Make the glaze:
Place the confectioners’ sugar in a small bowl. Rinse the lemon and pat it dry with a paper towel, then grate the yellow zest from the lemon into the bowl with the confectioners’ sugar. You should have about 2 teaspoons. Cut the lemon in half and squeeze the juice through a fine sieve into the bowl, discarding the seeds. You will get about 2 tablespoons of juice. Whisk the lemon juice and confectioners sugar together until the glaze is smooth. If there is not enough lemon juice, add 1 to 2 teaspoons of water to thin the glaze to a pouring consistency.
Using a wooden skewer, poke about 15 holes in the top of the cake. Slowly spoon the glaze over the cake, letting it soak into the holes before adding more. Slice and serve the cake while it is still warm or wait until it cools.