📖 Instructions

1. Preheat oven to 375°F (190°C). Lightly grease a 9x13 inch baking pan. I like to line mine with parchment paper, leaving an overhang for easy removal – makes things a breeze, trust me.
2. In a large mixing bowl, whisk together the flour, powdered sugar, and salt. Ah, the simple beginnings of something truly delicious. Kinda poetic, isn't it?
3. Cut in the cold butter using a pastry blender or a fork until the mixture resembles coarse crumbs. Seriously cold butter is key here – tiny pieces of butter coating the flour will give you that dreamy, flaky crust we all crave.
4. Add the egg yolk and vanilla extract. Mix until the dough just comes together. Don’t overmix it! Overworked dough means a tough crust, and nobody wants that. If it's too dry, a tiny splash of ice water can work wonders.
5. Press the dough evenly into the prepared baking pan. You might need to use your fingers or the bottom of a measuring cup to get it nice and even.
6. Bake the crust for 15-20 minutes, or until lightly golden. Keep an eye on it – ovens can be temperamental. You want it just set, not fully baked.
7. While the crust is baking, prepare the custard filling. In a separate mixing bowl, whisk together the granulated sugar, flour, salt, and lemon zest. That lemon zest adds such a bright, summery note, doesn't it?
8. In another bowl, whisk together the eggs, heavy cream, and vanilla extract. If you're feeling fancy, a splash of almond extract is delightful too.
9. Gradually whisk the wet ingredients into the dry ingredients until smooth. Make sure there are no lumps! A smooth custard is a happy custard.
10. Gently fold in the diced rhubarb. Now, be gentle with the rhubarb. We want it to stay in nice little pieces, not turn to mush. Though, honestly, even mushy rhubarb still tastes pretty good.
11. Pour the custard filling over the pre-baked crust. Spread it evenly. I sometimes like to arrange a few extra rhubarb pieces on top just for show.
12. Bake for 30-35 minutes, or until the filling is set and lightly golden. The center should be just slightly jiggly – it will firm up as it cools.
13. Let the bars cool completely in the pan before cutting into squares. This is the hardest part, I know. But patience is a virtue, and it pays off big time here. The bars will be much easier to cut cleanly once they're cool.
14. Dust with powdered sugar before serving, if desired. Okay, maybe *this* is the hardest part. Resisting the urge to eat the entire pan in one sitting. Good luck with that!