Preheat the oven to 360 F. Wash the peaches and cut into slices. Transfer half of the peaches to the bottom of a greased 9x13" baking dish.
Mix brown sugar and cinnamon in a bowl. Melt 4 tbsp butter and drizzle half of it on top of the peaches. Sprinkle half of the brown sugar and cinnamon mixture over that.
Beat the remaining softened butter with sugar until combined. Add cream cheese and beat for another minute on high speed. Add eggs one at a time, beating each time until combined.
Mix flour, baking powder and salt in a bowl. Add to the bowl with wet ingredients slowly. The result should be a thick dough without lumps, which will slowly drain from a spoon slowly.
Pour half of the batter on top of the peaches in the pan. Put the second half of the peaches on that batter, top with the remaining melted butter and sprinkle with cinnamon sugar.
Pour the remaining half of the dough over the top. Cover the baking dish with foil. Bake for 20 minutes. Remove the foil and bake for another 20 minutes.
Once a toothpick in the center comes out clean remove and let it cool for 15 minutes in the pan, then carefully put a platter on top covering the pan and invert the baking dish onto that or a cutting board works too.