Preheat the oven to 325°F. Spray a 10-12 cup bundt pan with baking spray that has flour in it, or brush the pan with softened butter using a pastry brush and dust with flour.
In the bowl of a stand mixer, beat butter and cream cheese on high speed for 2–3 minutes with the whisk or paddle attachment until creamy and smooth. Stop to scrape the bottom and sides of the bowl to ensure they are evenly mixed.
1 1/2 cups salted butter, 8 ounces cream cheese
Gradually add the sugar while the mixer is running and continue to beat the mixture until it is light, fluffy, and pale, about another 1-2 minutes on high speed. Mix in vanilla, then scrape the bottom and sides of the bowl again.
2 teaspoons pure vanilla extract, 2 1/2 cups (500g) granulated sugar
Add the eggs one at a time, mixing on low speed between each addition. Scrape down the bottom and sides of the bowl.
6 large eggs
Add the flour, baking powder, and salt, mixing on low speed just until the batter is starting to come together. It's okay if some streaks of flour still remain. Add the accumulated juices and sugars that have come off the diced peaches and mix that into the batter as well, scraping the bottom and sides of the bowl again.
3 cups (357g) cake flour, 1 teaspoon baking powder, 1/4 teaspoon salt
Gently fold in the chopped peaches. The batter will be thick.
Line the bottom of the prepared bundt pan with enough sliced peaches just to cover.
Pour half of the batter into the prepared pan. Sprinkle with all but 1/2 cup of the crumb topping. Add remaining batter and rap the pan against the counter a couple of times to remove any air bubbles.
Bake for 75–95 minutes in the preheated oven until a skewer comes out completely clean when inserted into the thickest part of the poundcake. Loosely cover the pan with aluminum foil halfway through baking to prevent the top from browning too much, if needed.
Cool in the pan for 10 minutes, then invert the bundt pan onto a cake plate or other serving plate. The cake should come right out, but if not, tap the pan firmly a few times with the butt end of a knife to help loosen it. Let cool completely before adding glaze.