Preheat the oven to 350°F. Lightly grease or line a 9x9-inch baking pan with parchment paper.
In a medium bowl, whisk the flour, baking powder, and salt until combined.
In a large mixing bowl, whisk the granulated sugar, brown sugar, and oil together. Then add the egg and vanilla, and whisk until combined.
Add the flour ingredients to the wet ingredients and mix just until combined. Don't overmix. The batter will be thick.
Gently fold in the peaches.
Spread the batter into the prepared baking pan.
In a small bowl, combine the streusel ingredients until crumbly. Sprinkle streusel over the batter in the baking pan.
Bake in a preheated oven for 25 minutes, or until a toothpick inserted into the center comes out clean.
Remove from the oven and allow to cool.
Whisk the glaze ingredients together and drizzle over the cake once cooled.