Heat your oven to 350°F. Grease a 9×9-inch baking pan and line the bottom with parchment paper.

Make the crust: Mix the flour, cornstarch, sugar, butter, and lemon zest until it looks like crumbly sand. Press this firmly into your prepared pan. Bake for 15 minutes until lightly golden. Take it out but leave the oven on.

Make the middle layer: Beat the cream cheese and sugar until it's fluffy (about 3-4 minutes). Add the egg and beat until smooth. Pour this over your warm crust.

Put it back in the oven for 10-15 minutes, just until the top sets a little bit. Take it out but leave the oven on.

Make the lemon layer: Whisk together the eggs, sugar, flour, and lemon juice. Gently pour this over the cream cheese layer, trying not to disturb it too much.

Bake again for 25-30 minutes until the center is just set (it shouldn't be jiggly).

Let it cool at room temperature, then put it in the fridge for at least 3 hours (overnight is even better).

Before serving, you can sprinkle some powdered sugar on top if you want. Cut into squares and enjoy!