Butter a 9×13 inch pan, or spray it with a nonstick spray. In a medium bowl, stir together sugar, baking powder, flour, salt and spices with a whisk.
Use a pastry blender, fork or your fingertips, incorporate softened butter and egg into the flour mixture. It will be crumbly. Pat 3/4 of the crumbs into the bottom of the prepared pan, pressing firmly. If the dough is too tacky to handle, chill for about 10 mins.
Tile peach slices over crumb base in a single layer, it’s ok if some overlap
Scatter remaining crumbs evenly over peaches and bake for 30 minutes, rotating halfway through, until top is slightly brown and you can see a little color around the edges.
Cool completely in pan before cutting into squares.