You may spot Sé Cathedral in the skyline before you actually find this important religious building. Step inside if the doors are open or just appreciate the facade from outside.
You're spoiled for sightseeing choice when in Panaji. Sé Cathedral is a great place to kick off here, but there are loads of other worthwhile sights to consider. Basilica of Bom Jesus, Church of Our Lady of Immaculate Conception, and Church of St. Cajetan are not far from the principal church and will round out your day nicely.