Preheat the oven to 350°.
Line the bottom of a 9 x 13 inch baking pan with parchment paper, leaving a bit of overhang along the long sides of the pan. You'll use this later to lift the bars from the pan.
Stir the crust ingredients together in a large mixing bowl, just until combined.
Press the mixture evenly into the bottom of your prepared baking pan (Note 1).
Place the pan into the oven and bake the crust for about 20 minutes, until golden brown. Transfer the pan to a cooling rack when it's done. Leave the oven on.
While the crust bakes, make the filling. Stir the lemon juice and cornstarch together in a small bowl or large liquid measuring cup. Make sure to fully dissolve the cornstarch.
Place the coconut cream and sugar into a small saucepan and set it over medium heat. Heat the mixture while whisking. After a few minutes the coconut cream will liquefy and the sugar will dissolve.
Once the coconut cream mixture comes to a simmer, whisk in the lemon juice mixture, then bring everything just back up to a simmer. It should begin to thicken up very quickly.
Remove the pot from heat as soon as the mixture begins to simmer and reaches the consistency of pudding.
Whisk in the lemon zest, lemon extract, salt, and turmeric or food coloring, if using.
Pour the filling over the crust when it comes out of the oven, spreading it out evenly.
Return the pan to the oven and bake the bars for 15 minutes more, until the filling becomes bubbly around the edges.
Remove the pan from the oven and transfer it to a cooling rack. Allow the bars to cool completely. The filling will continue to thicken up as it cools.
Remove the bars from the pan by carefully lifting the edges of the parchment paper. If you find the bars are sticking to the exposed sides of the pan, run a knife along these edges to loosen them.
Slice and optionally sprinkle the bars with powdered sugar (Note 2). Serve or store at room temperature in a sealed container for 2-3 days or in the refrigerator for up to 1 week (Note 3).