Combine all-purpose flour, unsalted butter, and Kosher salt in the bowl of a food processor fitted with blade attachment. Pulse until there are pea sized pieces of butter. Add cream cheese, then pulse a few additional times. Add ice water, then pulse again.
Turn the dough out onto a sheet of plastic wrap, then wrap and press it into a flat disk. Use your hands to help shape the dough so that it is flat and round. Refrigerate.
Preheat an oven. Lightly flour a work surface, then roll out the dough into a circle. Carefully transfer the dough to a parchment lined rimmed baking sheet. Refrigerate while you make the filling.
Place softened butter, large egg, almond flour (or almond meal), sugar, almond extract, and a pinch of Kosher salt in a large mixing bowl. Use a handheld mixer to whisk until well mixed. Refrigerate until needed.
Spread the frangipane filling onto the rolled out pastry dough. Spoon the rhubarb filling on top of the frangipane, being sure to scrape out the bowl. Fold the edges of the galette up and over onto itself, creating an overlapping crust.
Transfer to a preheated oven and bake until the filling is bubbling and the crust is golden brown. Allow the galette to cool until the filling is set, then slice and serve with chopped pistachios and whipped cream!