In a small bowl, combine the diced peaches, brown sugar, and cinnamon. Mix well and set aside to allow the peaches to macerate and release their juices.

Preheat your oven to 325°F (165°C). Grease and flour a 9-inch loaf pan or bundt pan to prevent sticking.

In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy. This should take about 3-5 minutes using an electric mixer.

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

In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet mixture, mixing just until combined.

Pour half of the batter into the prepared pan. Spoon the peach mixture evenly over the batter. Top with the remaining batter, spreading it gently to cover the peaches.

Bake in the preheated oven for 60-70 minutes, or until a toothpick inserted into the center comes out clean. Allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.