Preheat the oven to 350 degrees Fahrenheit and butter and flour a 4-inch cake pan.
For 3 minutes, beat together the butter and sugar until extremely light and fluffy. Beat in the egg for another minute before adding the dry ingredients.
Pour the batter into the prepared baking dish, spread it out, and bake for 20-23 minutes, or until a knife inserted into the middle comes out clean. Because oven temperatures vary and this is a little cake, check it after 20 minutes.
Remove your cake from the oven and allow it to cool fully before slicing it in half horizontally. It's simplest to accomplish this using a sharp bread knife!
Whip the cream, icing sugar, and vanilla extract until it forms medium peaks. Spread or pipe a layer of cream onto the bottom half of the cake, followed by a layer of jam and the remaining cake. Sprinkle with icing sugar and serve!