Preheat your oven to 350°F (175°C) and prepare two 8-inch round cake pans by greasing them thoroughly and lining the bottoms with parchment paper.

In a medium mixing bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, and nutmeg until evenly combined.

Cream together softened butter, granulated sugar, and brown sugar on medium-high speed for 3-4 minutes until light and fluffy.

Add eggs one at a time, beating well after each addition, then mix in vanilla extract.

Alternately add flour mixture and milk to butter mixture on low speed, beginning and ending with flour, mixing just until combined.

Gently fold in sour cream and diced peaches using a rubber spatula, being careful not to overmix.

Divide batter evenly between prepared pans and bake for 28-32 minutes until toothpick comes out clean.

Cool cakes in pans for 15 minutes before turning out onto wire racks to cool completely.

For frosting, melt butter in saucepan over medium heat, add brown sugar and cream, stirring until mixture boils.

Remove from heat and cool to room temperature (30-45 minutes).

Beat cooled mixture with powdered sugar one cup at a time, adding vanilla and salt until thick and spreadable.

Combine graham cracker crumbs with melted butter and brown sugar until texture resembles wet sand.

Place first cake layer on serving plate and spread one-third of frosting evenly across top.

Add second layer, apply thin crumb coat over entire exterior, and refrigerate for 20 minutes.

Apply remaining frosting generously over cake, creating textured swirls with offset spatula.

Press graham cracker mixture around bottom third of cake for decorative border.

Arrange fresh peach slices on top, pipe additional frosting rosettes if desired, and serve.