Every so often, a recipe becomes so entrenched in our family's history, it's a tradition all by itself. My mum's lemon squares are just that kind of recipe. These were her first choice for every school event, church function and sweet to have under the glass dome in the kitchen. Their simplicity makes these bars one of my favorites.
Preheat the oven to 350 degrees F. Line a 9-by-13-inch baking dish (I used a glass one) with parchment paper, leaving an overhang on two sides. Grease the parchment with butter.
For the crust: Using a food processor, or your hands in a large bowl, work together the flour, 2 sticks butter, and confectioners' sugar until a smooth dough forms. Spread the mixture on the bottom of the prepared baking dish and pat down so it's evenly distributed. Bake until lightly golden brown, 20 to 25 minutes. Remove the baking dish from the oven and set aside.
For the filling: Whisk together the eggs and granulated sugar in another large bowl until fully combined and a pale yellow hue. Add the lemon juice, lemon zest and vanilla and whisk to combine. Add the dry ingredients (flour, baking powder and salt) and whisk until just combined.
Pour the filling over the still hot crust and bake until the filling is just set, about 20 minutes. If you baked the crust ahead of time and it has cooled, bake for 35 to 40 minutes. Let cool and sprinkle with confectioners' sugar. Lift the bars out of the baking dish using the parchment overhang as handles. Cut into bars and garnish with little sprigs of rosemary, if you like. Enjoy!