Preheat the oven. Set it to 350°F (175°C). Lightly butter or spray a 9x13-inch baking dish.

Spread the lemon base. Pour the lemon pie filling into the dish and spread it evenly. Sprinkle the lemon zest over the top if using.

Make the cream cheese mixture. In a bowl, beat the softened cream cheese, sugar, vanilla, and a pinch of salt until smooth. It should be spreadable and creamy.

Dollop the cream cheese. Spoon the cream cheese mixture in small mounds across the lemon filling. You don’t need to cover every inch—pockets are good.

Add the dry cake mix. Sprinkle the cake mix evenly over the entire pan. Don’t stir.

Drizzle with butter. Slowly pour the melted butter over the cake mix, trying to moisten as much of the surface as you can. A few dry spots are fine; they’ll crisp up.

Bake. Place the dish on the center rack and bake for 40–50 minutes. The top should be golden and the filling should be bubbling around the edges. If spots look floury at 35 minutes, drizzle on 1–2 more tablespoons of melted butter and continue baking.

Rest before serving. Let the cake cool for at least 15–20 minutes so it can set slightly. Serve warm with whipped cream or ice cream.