In a mixing bowl, cream together unsalted butter and confectioner’s sugar until light and fluffy, about 3–4 minutes. Add one room-temperature egg and almond meal, mixing until fully incorporated. Gradually add plain flour until combined. Shape the dough into a disk, wrap in plastic wrap, and chill in the refrigerator for at least 1 hour to firm up.

Preheat your oven to 160°C (325°F). Roll out the chilled pastry dough on a lightly floured surface and carefully line a tart pan with it. Prick the base with a fork to prevent bubbling, then freeze for 10 minutes. Bake the crust for 20–30 minutes, or until golden brown. Allow it to cool completely before filling.

In a saucepan, heat whole milk and vanilla extract over medium heat until it begins to boil. Meanwhile, in a separate bowl, whisk together egg yolks, sugar, and cornstarch until smooth. Gradually blend the hot milk into the egg mixture. Return the combined mixture to the stove, whisking continuously until it thickens to the consistency of a custard, about 5–7 minutes. Refrigerate until cooled.

In a medium saucepan, combine water and sugar over medium heat. Once boiling, add the fresh rhubarb and simmer gently with lemon juice and your choice of spices until tender, about 8–10 minutes. Remove from heat and mash the mixture with a fork for a compote consistency. Allow it to cool.

Once the custard and rhubarb compote are cool, spread the creamy custard evenly over the baked tart shell. Next, spoon the rhubarb compote over the custard, creating a beautiful layered effect. Refrigerate the assembled tart for about 30 minutes to allow the flavors to meld.

When ready to serve, take the Sweet Rhubarb Custard Tart out of the refrigerator and let it sit at room temperature for about 10 minutes. This will enhance the flavors and make slicing easier. Cut into slices and enjoy the delightful combination of textures and flavors!