Cut the rhubarb into 1/2-inch pieces and place them in a saucepan with lemon juice, 3/4 cup allulose, and 3/4 cup water. Bring to a simmer over medium heat and cook for about 10 minutes until the rhubarb is completely soft and breaking down. Mash the rhubarb with a fork or blend briefly for 30 seconds to create a smooth sauce consistency. I find that a quick blend gives the filling a more elegant texture than mashing, but either works well depending on your preference for texture.

While the rhubarb cooks, sprinkle the gelatin over 1/4 cup cold water and let it sit for 2 minutes to bloom. Heat 1/2 cup water for about 30 seconds until hot, then pour it over the bloomed gelatin and stir well until completely dissolved and smooth. Pour the gelatin mixture into the cooked rhubarb sauce and stir thoroughly to combine. Transfer the mixture to a bowl and refrigerate for 2 to 3 hours until it reaches a thick, gel-like consistency but is still pourable.

Line a 9-inch pie pan with parchment paper. In a bowl, combine the nut flour, coconut flakes, 3/4 cup allulose (reserved for crust), and salt. Pour in the melted and cooled butter and mix until the texture resembles wet sand with no dry flour remaining. Press this mixture firmly and evenly into the bottom of your prepared pan, creating an even crust. Refrigerate the crust while you prepare the whipped cream topping.

Pour the heavy cream into a bowl and beat on high speed with an electric mixer until soft peaks form, about 2-3 minutes. Add 3 tbsp allulose and 1.5 tsp vanilla essence to the whipped cream and continue beating gently until just combined. I recommend adding a pinch of salt to the whipped cream as well—it balances the sweetness beautifully and makes the vanilla flavor pop. In a separate bowl, whip the coconut cream with 3 tbsp allulose and 1.5 tsp vanilla essence until it reaches a similar fluffy consistency; this creates a more complex topping with both dairy and coconut elements.

Remove the chilled crust from the refrigerator and pour the thickened rhubarb gel filling from Step 2 into the prepared crust, spreading it evenly. Top the rhubarb layer with the whipped cream mixture from Step 4, spreading or dolloping it generously across the surface. If desired, you can fold the coconut cream into the regular whipped cream for a swirled effect, or keep them as distinct layers. Refrigerate the finished pie for at least 30 minutes (or freeze for 30 minutes if you prefer a firmer texture) before serving to allow the layers to set together beautifully.