Simeon I of Bulgaria "adopts" the Hungarians instead of fighting them, and letting them to take the underpopulated Panonia. He takes Constantinople ( + Dyrachion and Thessalonika, and the European Greece and becomes ERE Emperor. The Bulgarian cultural identity is well advanced by then, and the Greek ERE citizen oppose the "Bulgarianization", thus Asia Minor breaks away as anti-ERE. The European / Balkan ethnic greeks move in Anatolia With non-land borders the two Empires are more secure in aspect with eachother and successfully share the Blacksea region repulsing the Turkic and other invasions...
Thus now Balkans are Bulgaria ( similary of how Iberia is - mostly - Spain ), and Anatolia is Greece. The Bulgarian "Portugal"-equivalent could be say, Albania ( but in the way Scotland and Wales are "separate nations" ), and the Greek ( Anatolian ) one - Syria, Armenia, Assyria ...