Preheat your oven to 350°F (175°C). Grease and flour a 9-inch round cake pan. Set aside.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

In a large bowl, cream together the softened butter and granulated sugar with an electric mixer until light and fluffy, about 3-4 minutes.

Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Mix in the vanilla extract.

Alternate adding the dry ingredient mixture and the buttermilk to the wet ingredients, beginning and ending with the dry mixture. Mix until just combined, being careful not to overmix.

Gently fold in the diced fresh peaches by hand.

Pour the batter into the prepared cake pan and bake for 40 to 45 minutes, or until a wooden skewer inserted into the center comes out clean.

Let the cake cool in the pan for 15 minutes before inverting it onto a wire rack to cool completely.

While the cake cools, prepare the glaze: Whisk together the powdered sugar, milk/cream, and lemon juice until smooth. Add more milk if a thinner glaze is desired.

Once the cake is fully cooled, drizzle the glaze evenly over the top and allow it to set before slicing and serving.