Vegetable oil spray for misting the pan
Flour for dusting the pan
1 package (18.25 ounces) plain yellow cake mix
1 package (3 ounces) lemon gelatin
2/3 vegetable oil, such as canola, corn, safflower, soybean, or sunflower
2/3 cup hot water
4 large eggs
1 cup confectioners' sugar, sifted
2 tablespoons fresh lemon juice (from 1 lemon)
1 teaspoon finely grated lemon zest (from 1 lemon)
Place a rack in the center of the oven and preheat the oven to 350 degrees F. Lightly mist a 12-cup Bundt pan with vegetable oil spray, then dust with flour. Shake out the excess flour. Set the pan aside.
Place the cake mix, gelatin, oil, water, and eggs in a large mixing bowl and beat with an electric mixer on low speed for 1 minute. Stop the machine and scrape down the sides of the bowl with a rubber spatula. Increase the mixer speed to medium and beat for 2 minutes more, scraping down the sides if needed. The batter should look thick and well blended. 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 light brown and just starts to pull away from the sides of the pan, about 40 minutes. Remove the pan from the oven and place it on a wire rack to cool for 10 minutes.
Meanwhile prepare the glaze Combine the confectioners' sugar, lemon juice, and lemon zest in a small bowl and stir with a wooden spoon until smooth.
Run a long, sharp knife around the edge of the cake and invert it onto a serving platter. Spoon the glaze evenly over the warm cake so that it drizzles down the sides and into the center. Slice and serve warm, or let it cool before slicing.
Store this cake, covered in plastic wrap or placed under a cake dome, at room temperature for up to 1 week. Or freeze it, wrapped in foil, for up to 6 months. Thaw the cake overnight on the counter before serving.