Preheat the Oven: Preheat your oven to 350°F (175°C). Grease a 9x13-inch (23x33 cm) baking pan or line it with parchment paper.
Mix Ingredients: In a large mixing bowl, combine the lemon cake mix, lemon pie filling, and eggs. Mix everything together until well combined and no dry cake mix remains.
Transfer to Pan: Pour the batter into the prepared baking pan, spreading it out evenly with a spatula.
Bake: Place the pan in the preheated oven and bake for approximately 25-30 minutes, or until the cake is set and a toothpick inserted into the center comes out clean.
Cool and Serve: Once baked, remove the cake from the oven and allow it to cool in the pan for about 10 minutes. Then, slice and serve as desired. Enjoy your delicious 3-Ingredient Lemon Cake!