Preheat the oven to 350°F (175°C) and grease a 9x13-inch baking dish.

Pour the dry yellow cake mix evenly into the prepared baking dish.

In a bowl, combine fresh lemon juice, lemon zest, granulated sugar, melted butter, and salt, stirring until the sugar begins to dissolve.

Bring 2 cups of water to a boil, then let it sit off heat for 30 seconds.

Pour the lemon mixture evenly over the dry cake mix without stirring.

Slowly pour the hot water over the lemon mixture from about 6 inches above the pan to distribute evenly.

Do not stir. Bake for 35 to 40 minutes, or until the top is golden brown and a toothpick inserted into the cake layer comes out clean.

Remove from the oven and let cool on a rack for at least 15 minutes before serving. Dust with powdered sugar if desired.