Lemon squares are the kind of treat I crave year round. They brighten up dull winter days and are equally refreshing when a heat wave hits in the summer. I’ve been using this Smitten Kitchen + Barefoot Contessa recipe for a few years now and they never fail to turn out AMAZING. Please be warned: like most good things, they require quite a bit of prep time, so make sure you have the energy and nothing to do for at least an hour. I like the tartness of regular lemons, but you can also try this with meyer lemons, or adding a little lime juice to mix it up. Here is Deb Perelman’s recipe, with a few slight variations (I mainly cut back on the sugar):
For the crust: 
1 cup unsalted butter, at room temperature
1/2 cup granulated sugar
2 cups flour
1/8 teaspoon kosher salt

For the lemon layer: 
6 extra-large eggs at room temperature
2 cups granulated sugar
2 tablespoons grated lemon zest (4 to 6 lemons)
1 cup freshly squeezed lemon juice
1 cup flour

Confectioners’ sugar, for dusting

Preheat the oven to 350°F and grease a 9 by 13 by 2-inch baking sheet.

For the crust, cream the butter and sugar until light in the bowl of an electric mixer fitted with the paddle attachment. Combine the flour and salt and, with the mixer on low, add to the butter until just mixed. Dump the dough onto a well-floured board and gather into a ball. Flatten the dough with floured hands and press it into the greased baking sheet, building up a 1/2-inch edge on all sides. Chill for about 15 minutes.
Bake the crust for 15 to 20 minutes, until just golden. Let cool on a wire rack for about 15 minutes, (you can keep the oven on).

For the lemon layer, whisk together the eggs, sugar, lemon zest, lemon juice, and flour. Pour over the crust and bake for 30 to 35 minutes, just until it’s set (make sure the centre isn’t too gooey). Let cool to room temperature. Cut into rectangles and dust with confectioners’ sugar using a fine mesh sieve. Enjoy!