Rose water, if you choose to use it, is available in Middle Eastern grocery stores and gourmet food shops. I like the sparkly look of turbinado sugar, which is golden and coarser, but regular granulated sugar works, too.
Make the dough
Combine the flour, cornmeal, salt, and 1 tablespoon of the sugar in a food processor; pulse briefly to combine. Add the butter; pulse until the mixture is the texture of coarse meal. Transfer to a medium bowl. In a small bowl, beat together the egg yolk and sour cream. Stir this mixture into the dough, using a fork to blend. Gather the dough into a ball, wrap it in plastic, and compress into a disk. Chill for at least 1 hour but no longer than a day.
Assemble the tart
Position oven racks on the middle and bottom rungs and heat the oven to 375°F. Remove the dough from the refrigerator and let it sit for 10 minutes or so to take the chill off (you'll want it to roll without cracking). On a lightly floured surface, roll the dough into a 15-inch round. Transfer to a rimmed baking sheet lined with parchment. In a small bowl, combine the remaining 1/2 cup sugar, the cornstarch, and the cinnamon. Put the raspberries in a medium bowl and sprinkle with the sugar mixture. Add the rose water, if using; and toss very gently to combine the ingredients. Pile the filling in the center of the dough circle, leaving a 2-1/2-inch border all around. Pleat the tart, being careful not to rip the dough. Brush the cream onto the edge crust and sprinkle with the turbinado sugar. Bake on the middle rack for 20 minutes. Move the tart to the bottom rack, reduce the oven temperature to 350°F, and bake for another 25 to 30 minutes, rotating the pan if needed, until the crust is golden brown.
Photo: Amy Albert