Make the Crumb Layer: Melt the butter in a medium bowl. Whisk in the sugars. Stir in the remaining crumb ingredients until you have large crumbs. If the mixture seems to wet, don't fret - it will stiffen up as the butter begins to re-solidify at room temperature.

Prepare the Peaches: Stir together the corn starch and water until dissolved. Set aside. Add the peach slices, sugar, cinnamon, nutmeg, and lemon juice to a medium saucepan over medium heat. Cook, stirring gently, for 5 minutes. Re-stir the corn starch slurry so it's all dissolved, then add to the peach mixture and continue cooking for 30-60 seconds, until the juices have thickened. Remove from the heat and stir in the vanilla extract. Transfer to bowl to cool completely (you can speed this up in the fridge). Extra Peaches For Serving: If you want to add extra peaches on top of the cake for serving (pictured), make 1.5x the amount of peach topping. You'll either need to put a small piece of parchment or wax paper under the peaches on top of the cake to prevent excess moisture from seeping in, or add the extra topping to individual slices as they're being served.

Make the Cake Batter: Add the eggs to a large mixing bowl and beat with an electric mixer for 30 seconds on medium high speed. Add sugars and beat on medium high speed until the mixture is pale and thick, 1 minute. Whisk in the oil, sour cream, and vanilla. Add the dry ingredients and begin folding in with a silicone spatula until halfway incorporated, then pour in the milk. Continue gently folding together just until the last streaks of flour disappear into the batter. If there are a few lumps, that's fine.

Make the Cinnamon Sugar Ripple: Stir together brown sugar and cinnamon in a small bowl until well combined.

Assemble & Bake: Preheat your oven to 350° F. Spray a 9-inch springform pan with nonstick spray and place a piece of parchment paper across the bottom before securing the sides. Then, use a thinner strip of paper to line the sides of the pan - if it sticks out the top some, that's fine. Pour half the cake batter (430 grams if you want to be perfectly precise, haha) into your prepared pan, then sprinkle on the cinnamon sugar ripple. Dollop the remaining batter on top, and gently spread to even it out. Spoon the peaches, leaving behind the juices, over the batter. Sprinkle on the crumb mixture last. Bake for 50 to 58 minutes. The crumb will be deeply golden brown and a cake tester inserted into the center of the cake will pull out moist crumbs.

Make the Glaze: While the cake bakes, whisk together the glaze ingredients in a small bowl. Adjust thickness by adding more powdered sugar (thicker) or more milk/water (runnier). Add more cinnamon if desired, to taste.

Serve + Store: Let cake cool to your liking or enjoy warm! Do give it about 10 minutes to rest before removing the pan and adding the glaze. Slice and enjoy! Store leftovers in an airtight container in the fridge for 2-3 days.