Preheat oven to 175 degrees Celsius (350 degrees Fahrenheit). Butter 2 5-inch cake pans and line the bottom with parchment paper. Set aside.
Combine flour, corn starch, baking powder, baking soda and salt in a small bowl. Set aside.
Place butter, caster sugar and brown sugar in a large mixing bowl and beat with an electirc mixer until light and fluffy, scrapping down the sides occasionally. Beat in the egg and vanilla until combined then beat in the milk and peach purée. Sift in the flour in 2 batches and beat on low speed until just combined. Stir in the diced peaches.
Divide the cake batter between the 2 cake pans and bake for 35 to 40 minutes, until a skewer inserted into the center of the cake comes out clean. Place the cake pans on a wire rack and cool completely before frosting.
Peach-Vanilla Buttercream
Beat butter and icing sugar together until creamy. Add in peach purée, vanilla and salt and beat until combined. Taste the frosting and add more sugar if desired. (I used only 60 grams icing sugar.)
Fruit Glaze
Combine sugar and lemon juice in a small pot and bring to a simmer over low heat. Dissolve corn starch into the water and add into the pot. Stir until the glaze has thickened. Remove from heat and set aside to cool completely before using.
Assembly
Run a spatula along the edges of the cake pans and carefully unmould the cakes. Place one cake layer right-side up (see step-by-step photos) and spread with 1/2 of the buttercream, with the sides thicker than the center.
Place the second cake layer upside down on top of the first cake layer and frost the top with remaining buttercream. Place the peach dices in the middle of the cake and brush the glaze on top before serving.
NOTES
- To make the peach purée: Peel and core the peaches. Blend the peaches until fine and strain the mixture. 4 peaches will yield around 1 cup of peach purée, so for this recipe, you will need to purée 3 peaches.- To frost the whole cake, triple the frosting recipe. - This recipe can be made into cupcakes (makes about 12). Double the frosting recipe to make enough to frost the cupcakes. Credits - Cake recipe adapted from Smitten Kitchen's Peach Cupcakes - Buttercream recipe adapted from Cathlin Cooks' Peach Buttercream - Glaze recipe adapted from Food.Com