Preheat oven to 350 degrees. Place sliced almonds in a single layer on a rimmed baking sheet. Toast until they are fragrant, about 5 minutes. Transfer to a wire rack to cool. Use 1 tablespoon melted butter to coat six 4 1/2-by-1 3/4 inch round baking dishes, and set aside.
Place flour, 2/3 cup sugar, salt, and almonds in the bowl of a food processor fitted with the metal blade; pulse until mixture is finely ground. Transfer to a medium bowl. Add eggs, egg yolks, 3/4 cup cream, vanilla scrapings, and lemon zest, and whisk to combine. Place in refrigerator, and let rest 30 minutes.
Place cherries in a medium bowl; add kirsch, if using, and let macerate 30 minutes. Divide among dishes. Whisk remaining butter into batter; pour batter over cherries, and place dishes on a rimmed baking sheet. Bake 20 minutes. Sprinkle with remaining sugar; bake until tops are golden and bubbling, 15 to 20 minutes. Transfer to a wire rack to cool.
Whip remaining 1/2 cup cream until soft peaks form. Serve clafoutis warm or at room temperature, topped with whipped cream.