Coconut Custard and Rhubarb Tart

Bring coconut milk to a simmer in a medium saucepan. Whisk egg yolks, sugar, cornstarch, and salt in a medium bowl to combine. Whisking constantly, gradually add 1 cup warmed coconut milk to egg yolk mixture. Whisking constantly, add egg mixture to milk mixture in saucepan. Cook over medium heat, whisking constantly, 7 minutes (mixture should start bubbling halfway through and thicken to a pudding consistency, but be sure to cook the full 7 minutes).

Strain mixture through a fine-mesh sieve into a large bowl. Immediately whisk in coconut oil and vanilla. Cover bowl with plastic, pressing on surface of custard. Chill until set, at least 2 hours.

Do Ahead: Custard can be made 1 day ahead. Keep chilled.

Preheat oven to 325°. Toast coconut on a rimmed baking sheet, tossing once, until golden, 7–10 minutes. Let cool.

Lightly coat tart pan with nonstick spray. Mix toasted coconut, egg whites, oil, sugar, and salt with a rubber spatula in a large bowl until combined and the consistency of a stiff paste.

Transfer coconut mixture to tart pan. Using your hands, press mixture evenly onto bottom and up sides of pan. Bake crust until edges are lightly brown and bottom is set and just barely golden, about 10 minutes. Transfer pan to a wire rack and let crust cool.

Do Ahead: Crust can be baked 1 day ahead. Wrap with plastic and store at room temperature.

Sprinkle gelatin over 1/4 cup water in a small bowl. Let sit 10 minutes.

Combine jelly and 1 cup water in a medium saucepan and bring to a boil. Add bloomed gelatin and mix to combine. Add rhubarb, reduce heat, and simmer, stirring occasionally, until rhubarb is lighter pink in color and slightly softened, 2–4 minutes depending on thickness of stalks. Mix in lemon juice. Turn off heat and let rhubarb come to room temperature in syrup (about 1 hour). Strain cooled rhubarb through a fine-mesh sieve into a small bowl; reserve syrup.

Whisk chilled custard until creamy. Spoon custard into tart shell; smooth with an offset spatula.

Scatter rhubarb in an even layer over custard. Pour 1/4 cup rhubarb syrup over fruit, tilting pan to evenly distribute. Chill 20 minutes, then repeat with 1/4 cup rhubarb syrup. Chill tart at least 3 hours and up to overnight before serving.