Cake Batter:

• 2 cups all-purpose flour
• 1 teaspoon baking powder
• 1/2 teaspoon baking soda
• 1/4 teaspoon salt
• 1 cup (2 sticks) unsalted butter, softened
• 1 cup granulated sugar
• 1/2 cup packed light brown sugar
• 2 large eggs
• 1 teaspoon vanilla extract
• 1/2 cup buttermilk

Peach Topping:

• 4 ripe peaches, peeled and sliced (about 4 cups)
• 1/4 cup packed light brown sugar
• 2 tablespoons unsalted butter, melted
• 1 teaspoon ground cinnamon
• 1/4 teaspoon ground nutmeg

Streusel Topping:

• 1/2 cup all-purpose flour
• 1/4 cup packed light brown sugar
• 1/4 cup cold unsalted butter, cut into small pieces
• 1/4 cup chopped pecans or walnuts (optional)
• 1/4 teaspoon ground cinnamon