Place the softened butter pieces and the caster sugar into a planetary mixer bowl fitted with a whisk, turn on the whisk to mix the ingredients until they are creamy, then add the eggs, the vanilla seeds, and the sifted flour and baking powder.
Pour the milk in slowly while whisking. Wash and peel the peaches and cut into wedges. Spread the caramel across the base of a 28 cm baking tin with a slightly buttered and floured scalloped edge, then lay the peach slices in a spiral pattern across the base of the tin and then sprinkle the surface with the crushed macaroons. At this point, pour the cake batter over the peaches, smooth out with a spatula and bake at 180°C for 45 minutes (or in a convection oven at 160°C for 35 mins). When cooked, remove from the oven, allow to cool and then turn upside down onto a serving dish. Your peach and macaroon upside-down cake is ready to delight all!