Preheat the oven to 350°F (180°C). Grease two 8-inch (20 cm) round cake pans with butter and line the bottoms with parchment paper.

In a medium bowl, whisk together the flour and baking powder (omit if using King Arthur flour).

In the bowl of a stand mixer fitted with a paddle attachment (or using a handheld electric mixer), cream the butter and sugar on medium-high speed for 2-3 minutes until pale and fluffy. Scrape down the bowl.

With the mixer on low speed, add the eggs one at a time, fully incorporating each before adding the next. Scrape down the bowl and mix in the milk and vanilla extract until well combined.

Divide the batter evenly into the prepared cake pans and smooth out the tops. Bake for 20-23 minutes until the tops are golden brown and a cake tester inserted into the center comes out clean.

Cool in the pans for 10 minutes then invert the cakes onto a wire rack to cool completely before adding the cream (about 30 minutes).

Wash and thinly slice the peaches. Add them to a medium bowl with the sugar and toss to evenly coat the peaches. Let sit at room temperature for at least 30 minutes until syrupy.

Add the mascarpone, powdered sugar, heavy cream, and vanilla extract to a large bowl. Using an electric hand mixer, whip on low speed until fluffy and spreadable.

Place one cake layer onto a serving plate or cake stand. Spoon a generous amount of the peach syrup onto the cake then spread on half of the cream using an offset spatula.

Arrange one layer of the sliced macerated peaches on the cream then add a small ring of cream on top of the peaches (see post for visual). This acts as a "glue" to hold the layers together. Place the second cake on top and gently press down.

Spoon more of the peach syrup onto the cake layer. Spread the remaining mascarpone cream on top and arrange the rest of the peaches in the center of the cake. Spoon any remaining peach syrup over top then slice and enjoy!