Getting the Axis aligned Bound Box of an item is has transformations (rotation, scaling,...)

I need to find a way to retrieve the AABB of an item that works even if it has transformations applied. I thought anchors was always AA, but left can look to bottom with a rotation of -45 degrees. I need something precise to be able to place other elements correctly. I tried with a component but it’s not really easy to implement and there is a lot of hacks without success.