Preheat the oven to 350-degrees. Spray a 9” x 13” baking pan with a cooking spray, line it with a sheet of parchment, and spray the parchment paper.
To make the cake:
Beat the butter on medium speed until very creamy, about 2 to 3 minutes.
Slowly add the sugar and continue beating on medium speed until the butter and sugar are light and fluffy, about 3 minutes. Scrape the sides and bottom of the bowl about halfway through.
Add the whole eggs one at a time, beating in on medium speed.
In a medium mixing bowl, whisk together the flour, baking powder, and the kosher salt.
Stir in half the flour on low speed, mixing just until the flour disappears.
Add both egg yolks, blending in on low speed.
Toss in the remaining flour and blend into the batter on low speed. Scrape the sides and bottom of the bowl to make certain the batter is mixed well.
Add the vanilla extract.
Spread the batter into the bottom of the pan spreading as evenly as possible. It will be a thin layer.
Scatter the chopped peaches over the top of the batter.
To make the crumb topping and finish the cake:
In a small bowl, whisk together the flour, brown sugar, cinnamon, nutmeg, and chopped pecans.
Pour in the melted butter and stir until well combined. The topping will come together in large “crumbles”.
Sprinkle the crumb topping over the peaches.
Bake at 350-degrees for 40 minutes or until the cake tests done when a toothpick is inserted in the center. Take care not to over bake.