Preheat oven to 400°. Line bottom of a 9-inch springform pan with parchment paper, and spray with baking spray with flour.
For cake: Combine flour, sugar, baking powder, salt, and nutmeg in a mixing bowl, and stir well with a whisk.
In a heavy-duty mixing bowl, beat butter with a mixer at medium speed until creamy. Add flour mixture, and beat 1 minute more. Add milk and egg, and beat until well blended. Spread mixture into bottom of pan. Top with peaches. Bake for 15 minutes.
For custard cream: In a medium bowl, whisk cream and flour until smooth. Add sugar, egg, vanilla extract, and salt, whisking until smooth.
Remove cake from oven, and pour custard cream on top.
Return cake to oven, and reduce temperature to 350°. Bake, covering loosely with foil after 30 minutes to prevent overbrowning. Continue baking until cake top is puffed and edges are deep golden and starting to separate from pan, 5 to 10 minutes more. Let cool in pan for 15 minutes; remove from pan and let cool completely. Garnish with flowers, if desired.
Recipe by Victoria at https://victoriamag.com/peach-kuchen-recipe/