Preheat the oven to 350°F (175°C). Spray a 9×13 inch baking dish with non-stick cooking spray and set aside.

In a large mixing bowl, whisk together the flour, sugar, baking powder, cinnamon, and salt until well combined.

In a small bowl, add the eggs and oil. Stir until well combined.

Add the egg and oil mixture to the flour mixture, mixing until just combined. The batter should be slightly lumpy; avoid overmixing!

Gently fold in the diced peaches with a spatula until evenly distributed in the batter.

Carefully pour the batter into the prepared baking dish, spreading it out evenly.

In a medium bowl, whisk together the flour, cinnamon, and confectioners' sugar for the crumble topping. Stir in the melted butter until a crumbly dough forms.

Sprinkle the crumble topping evenly over the peach batter.

Bake in the preheated oven for 55-60 minutes, or until a toothpick inserted in the center comes out mostly clean with a few crumbs stuck to it.

In the last few minutes of baking, heat the milk, butter, and sugar in a small saucepan over medium heat, stirring until the butter and sugar have dissolved.

Once the cake is done, remove it from the oven and insert a skewer into the top, making 25-30 evenly spaced holes all the way to the bottom.

Carefully pour the milk mixture over the cake, ensuring it fills the holes and covers the top for extra moisture.

Let the cake cool completely in the baking dish on a wire rack.

For the glaze, whisk together the confectioners' sugar and milk until smooth. If it's too thick, add more milk one teaspoon at a time until you reach your desired consistency.

Drizzle the glaze over the cooled cake, slice, and serve!