Preheat the oven to 350°F with a rack in the center. Lightly grease a 9" x 13" pan. (If you plan to serve the peach Melba cake outside of the pan, line with a parchment sling so you can easily remove it once baked and cooled. Lightly grease the sling.), To prepare the fruit: Slice the peaches into 1/2"-thick wedges; you should have about 4 cups (595g). In a large bowl, combine the peaches, sugar, lemon juice, and salt. Stir to combine and set aside., To prepare the cake: In a large bowl, whisk together the flour, sugar, baking powder, and salt. Using your fingers or a pastry blender, work the butter into the flour mixture until it resembles a coarse meal. (If using a stand mixer, mix on low speed for 30 to 60 seconds.), Add the eggs, milk, and extract, and use a flexible spatula to stir the ingredients together into a thick batter (you might see some small specks of butter, that’s OK)., Transfer the batter to the prepared pan and spread into an even layer; a small offset spatula is a helpful tool here., Arrange 1 1/2 cups (about 255g) of the peaches and 3/4 cup (90g) of the raspberries evenly on top of the batter. Let the remaining peaches continue macerating while the cake bakes and cools., Bake the cake for 40 to 45 minutes, until the center springs back lightly when touched and the top is light golden brown. A toothpick or thin knife inserted into the center of the cake should come out clean when it's done. , Allow the cake to cool completely in the pan on a wire rack., To make the whipped cream: Just before serving, add the cream, confectioners’ sugar, and extract to a large bowl or the bowl of a stand mixer. Whisk until stiff peaks form. (Alternatively, see this blog post for details on how to make Mason jar whipped cream.), If you expect the cake to be eaten the same day, spread the whipped cream evenly over the top of the cake, leaving an exposed border of cake, if desired. Spoon the remaining peaches and some of their juices over the top and garnish with additional raspberries. Alternatively, serve slices of cake with dollops of whipped cream or scoops of vanilla ice cream on top. Spoon over the remaining peaches and some of their juices. Top with remaining raspberries., Storage instructions: Refrigerate any leftover peach Melba cake and fruit topping, stored in separate covered containers, for up to 4 days.