Preheat the oven to 350°F and line a 9×9-inch pan with parchment paper.

In a large bowl, beat the butter and sugar for 2–3 minutes, until light and fluffy.

Mix in the vanilla extract, then add the flour and mix just until a soft dough forms.

Press the dough evenly into the prepared pan, smoothing the top with a spatula or spoon.

Bake for 19–20 minutes, until the edges are lightly golden.

While the crust bakes, whisk together the eggs, sugar, and flour for 1–2 minutes, until smooth.

Zest the lemon directly into the mixture.

Juice 3–4 lemons (about ⅔ cup juice), removing any seeds, and whisk into the filling until fully combined.

Remove the crust from the oven and immediately pour the lemon filling over the hot crust.

Return the pan to the oven and bake for about 20 minutes, or until the filling is set.

Allow the lemon bars to cool, then refrigerate for 2–3 hours to fully set.

Before serving, dust generously with powdered sugar.

Store lemon bars in the refrigerator for up to 8 days.