OK, I'll try this, and I'll try to come up with a single POD too.
The East Romans establish a secure hold over all of Italy, most likely do to Justinian's Wars being much more successful. You can have Justinian's wars in Italy being more successful with quite a few PODs, though no plague probably works best. The Lombards are either kept out, or more likely, absorbed within the East Roman system. There is no intervention in Spain, though this is less important.
Note that Justinian did very well to get what he got, a completely reversal at the hands of the Ostrogoths was more likely, but it was just possible for the East Roman conquest to be more successful.
Secure East Roman hold over the entire Italian peninsula produces a ton of butterflies that leaves the Middle Ages unrecognizable. One of the earliest is that Heraclius might give up fighting the Persians for Anatolia and retreat to there. But lets say that doesn't happen. They Byzantines get no Venice, no Italian maritime/ pirate cities, no Norman pirate kingdom in southern Italy, the tax revenue from Italy, and more manpower. There is no Holy Roman empire in this Middle Ages. This isn't a complete Byzantine wank, since they have to spend much more effort on Italian affairs and may lose the cities anyway like the Hohenstaufen did. But they are strengthened enough to hold on to or retake Anatolia. And no Crusades helps alot too.
To get a stronger Muslim hold on Spain is harder, but here no Crusades helps. The Visigoths are more fragile and the Franks are weaker and more focused on confronting Constantinople. Western Christians don't care that much about the requonquista, and may even ally with the Spanish Muslims against the Byzantines. And the Normans are hired as mercenaries by the Caliphs/ Emirs of al-Andulas. Maybe some of the ghazis who kicked the Byzantines out of Analtolia wind up in Spain too.