You can apply lid on planer faces with flow sim. lid command. However you can create manually.
As mentioned, lids are strictly planar. If you wish to create a spherical lid, you would need to create the part manually. If your simulation is in an assembly, then make a new part and mate it into position. If the simulation is a multibody part, then insert a new part and draw it in context to your orifice. While lids are planar, boundary conditions are not so you can use that spherical body as an inlet/outlet.
can you post a picture of your model and give a bit more information about what BC will be applied to the lid and why it needs to be spherical?
like michael said, you have to take into account the BC that will be applied on a spherical face