In a medium bowl, combine flour, dark brown sugar, and room temperature butter. Mix until the mixture resembles coarse crumbs, about 5 minutes.

In a large mixing bowl, sift together all-purpose flour, baking powder, and salt. Stir in granulated sugar until everything is just combined.

In a separate bowl, beat the room temperature butter until sandy. Add in eggs, Greek yogurt, vegetable oil, and vanilla extract, mixing until smooth.

Chop the fresh peaches into small pieces and toss them in cornstarch. Gently fold about a third of the peaches into the wet batter.

Pour the batter into a prepared springform pan. Top with the remaining chopped peaches and sprinkle the prepared crumble evenly over the top.

Place the springform pan in a preheated oven at 350ºF and bake for 45-55 minutes.

While the cake cools, whisk together powdered sugar, water, vanilla extract, and Greek yogurt until smooth.

Once the cake has cooled slightly, carefully remove it from the springform pan. Drizzle the glaze over the top and allow it to set before cutting into slices.