Making Peach Cake with Brown Sugar Frosting is straightforward if you follow these clear steps:

1. Preheat Oven: Preheat your oven to 350°F (175°C). Grease and flour a 9×13 inch baking pan.

2. Mix Dry Ingredients: In a large bowl, sift together the flour, baking powder, baking soda, and salt.

3. Cream Butter and Sugar: In another bowl, cream the unsalted butter and granulated sugar until light and fluffy.

4. Add Eggs and Vanilla: Beat in the eggs one at a time, then stir in the vanilla extract.

5. Combine Dry and Wet Ingredients: Gradually add the dry ingredient mixture to the butter mixture, alternating with whole milk. Mix until just combined.

6. Fold in Peaches: Gently fold in the diced peaches, ensuring they are evenly distributed throughout the batter.

7. Pour and Bake: Pour the batter into the prepared baking pan. Bake for 30-40 minutes, or until a toothpick inserted in the center comes out clean.

8. Cool: Once baked, remove from the oven and let the cake cool in the pan for about 20 minutes. After cooling, transfer to a wire rack to cool completely.

9. Prepare Frosting: In a medium bowl, beat the unsalted butter and brown sugar together until smooth. Gradually add powdered sugar, milk, and vanilla extract, mixing until creamy and fluffy.

10. Frost the Cake: Once the cake is completely cool, spread the brown sugar frosting evenly on top of the cake. You can also reserve some frosting for decorating, if desired.