📖 Instructions

1. Preheat your oven to 350°F (175°C). Lightly grease a 9x13 inch baking pan and line it with parchment paper, leaving an overhang on the sides for easy removal.
2. In a food processor, combine the macadamia nuts, flour, powdered sugar, and salt. Pulse until the nuts are finely ground and the mixture resembles coarse crumbs. If you don't have a food processor, finely chop the nuts and mix them with the other dry ingredients.
3. Add the cold butter, cut into small cubes, to the food processor. Pulse until the mixture forms a dough that starts to clump together. Be careful not to over-process, or the crust will be tough.
4. Press the dough evenly into the bottom of the prepared baking pan. Use the bottom of a measuring cup to smooth it out and ensure it's packed tightly.
5. Bake the crust for 15-20 minutes, or until it's lightly golden brown. This step is called blind baking and helps prevent the crust from becoming soggy when you add the filling. Let it cool slightly while you prepare the custard.
6. In a large mixing bowl, whisk together the granulated sugar, cornstarch, and salt. This ensures the cornstarch is evenly distributed, preventing lumps in the custard.
7. In a separate bowl, whisk together the eggs and egg yolks until they are light and frothy. This will help create a smooth and creamy custard.
8. Gradually whisk the egg mixture into the sugar mixture, mixing until well combined. Make sure there are no lumps.
9. In a saucepan, heat the milk and heavy cream over medium heat until it just begins to simmer. Be careful not to boil it.
10. Slowly pour the hot milk mixture into the egg mixture, whisking constantly to temper the eggs. This prevents the eggs from scrambling.
11. Pour the custard mixture back into the saucepan. Cook over medium heat, stirring constantly with a rubber spatula, until the custard thickens enough to coat the back of the spatula. This should take about 5-7 minutes. Be patient and keep stirring to prevent scorching.
12. Remove the custard from the heat and stir in the vanilla extract and lemon zest. The lemon zest adds a nice brightness to balance the sweetness.
13. Gently fold in the chopped rhubarb. Make sure the rhubarb is evenly distributed throughout the custard.
14. Pour the rhubarb custard filling over the pre-baked macadamia crust. Spread it evenly.
15. Bake in the preheated oven for 25-30 minutes, or until the filling is set but still slightly jiggly in the center. The edges should be lightly golden brown.
16. Let the bars cool completely in the pan on a wire rack. Then, refrigerate for at least 2 hours before cutting into squares. This allows the custard to set fully and makes the bars easier to cut.
17. Before serving, dust the bars with powdered sugar, if desired. Lift the bars out of the pan using the parchment paper overhang. Cut into squares and enjoy! You can add a dollop of fresh cream to elevate the dessert.
18. Clean up your used equipment to enjoy your freshly made Macadamia Crust Rhubarb Custard Bars.