To make the peanut butter crumbs, whisk together brown sugar, granulated sugar, cinnamon, salt, and flour in a medium-sized bowl. Add peanut butter and melted butter. Use a rubber spatula to stir ingredients until mostly combined, then use clean hands to mix ingredients until completely combined and crumble into crumbs. Set aside.

Preheat oven to 350°F and spray a 9-inch springform pan with baking spray with flour.

To make the cake, whisk together flour, sugar, baking powder, cinnamon, and salt in a large bowl. Add eggs and vanilla. Mix on medium speed with an electric mixer until combined. Add oil, creamy peanut butter, and milk. Mix until all ingredients are completely combined, 1 to 2 minutes.

Pour batter into the prepared pan. Sprinkle crumbs evenly over the top and slightly press into the batter. Bake for 50 to 55 minutes, tenting pan with foil about halfway through baking to prevent the crumbs from over baking. Check for doneness by inserting a wooden pick into the center of the cake. If it comes out clean or with only a couple of crumbs, it’s done, Let cake cool completely.

To make the glaze, stir together hot water and peanut butter to make peanut butter easy to incorporate into the powdered sugar. In a small bowl, combine powdered sugar, peanut butter mixture, vanilla, and milk. Whisk until smooth. Drizzle over crumb cake and let the glaze set 5 to 10 minutes. Use a serrated knife to cut into slices.