Preheat oven to 350°F (≈175°C). Grease or line a 10" springform pan.
Mix dry ingredients: 2 cups flour, baking powder, cinnamon. Set aside.
In another bowl, beat milk, brown sugar, sour cream, softened butter, egg, and vanilla until creamy.
Stir the dry ingredients into the wet just until blended. Fold in sliced peaches.
Spoon batter into prepared pan. Prepare crumb topping by combining brown sugar and flour; cut in cold butter to form crumbs. Sprinkle over batter.
Bake 50–55 minutes (or until center is set and top is golden).
Let cool slightly; mix glaze ingredients and drizzle over warm cake.
Slice, serve, and enjoy.