Preheat your oven to 325°F (160°C). Grease and flour a 10-inch Bundt pan or a 9x13 inch baking pan.

Make the peach filling: In a medium bowl, combine the sliced peaches, 0.5 cup granulated sugar, cornstarch, cinnamon, nutmeg, and lemon juice. Toss gently to coat the peaches evenly. Set aside.

Make the pound cake batter: In a large bowl, cream together the softened butter and 1.5 cups granulated sugar until light and fluffy. Beat in the eggs one at a time, followed by the vanilla extract.

In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk, beginning and ending with the dry ingredients. Mix until just combined. Do not overmix.

Assemble the cake: Pour about half of the pound cake batter into the prepared pan. Spoon half of the peach filling evenly over the batter. Top with the remaining batter, spreading gently. Spoon the remaining peach filling over the top of the batter. Swirl lightly with a knife or skewer, being careful not to mix too deeply.

Bake for 60-70 minutes, or until a wooden skewer inserted into the center of the cake comes out clean. If the top begins to brown too quickly, tent loosely with foil.

Let the cake cool in the pan for 15-20 minutes before inverting it onto a wire rack to cool completely.