How to Make It
Preheat the oven to 350°. Butter a 9-inch springform pan. Spread the almonds on a baking sheet and toast for 10 minutes, until golden. Let cool slightly, then coarsely chop the almonds. Leave the oven on.
In a small bowl, mix the egg yolk with the orange zest and the extracts. In a medium bowl, mix the flour, cornmeal and salt. Cut in the butter with a pastry blender or rub it in with your fingers until the mixture resembles coarse meal. Stir in the granulated sugar and brown sugar and the toasted almonds. Gently work in the egg yolk mixture with your hands; the dough should be crumbly.
Transfer the dough to the prepared pan and loosely press the crumbs; the surface should be uneven. Bake for 40 minutes, or until deep golden brown. Transfer to a rack and let cool completely before unmolding.
Break the tart into large pieces. Pile on a platter with the Roasted Red Grapes and serve with the Champagne Sabayon.