Preheat the oven to 350β/180β. For easy removal of the cake, place parchment paper on the bottom and 2 sides of the pan. Gently grease the two sides without parchment paper and then set aside. Dice the peaches, about 2 cups total.
2 cups diced peaches
In a medium sized bowl, add in flour, cornstarch, baking soda, baking powder, and salt. Stir to combine and set aside.
In a large bowl, add softened butter and white sugar. Beat on medium speed for 2-3 minutes until itβs light and fluffy. Make sure to scrap the sides of the bowl.
1/2 cup butter, 1 cup white sugar
Add in the egg, egg yolk, vanilla, and yogurt. Continue mixing on medium speed until smooth.
1 egg, 1 egg yolk, 1 tbsp vanilla, 2/3 cups yogurt or kefir or buttermilk*
Mix in the dry ingredients and using a spatula, gently fold until a batter forms. Do not overmix!
Gently toss the diced peaches in 1 tbsp of flour before adding them into the mixing bowl. This will help absorb any liquid they may have from washing. Then add into the bowl and mix in a few times.
Spread the batter into the prepared pan evenly and sprinkle extra white sugar on top. This will give you a sweet crunchy top.
Bake for 35-45 minutes, depending on your oven. It took me 45 minutes. Allow it to cool, slice, and enjoy!
This cake is best eaten day of or next day. Store it in the fridge for up to 5 days in an airtight container.
Notes
Buttermilk* To make buttermilk, stir 2/3 cups of milk with 2 tsps of lemon juice or vinegar. Allow to sit on your counter for at least 10 minutes before using.