In Ephesians 2:20, God's household is built with Christ Jesus Himself as what?

Answer: The cornerstone

Believers are built on the foundation of the apostles and prophets, with Christ Jesus Himself as the cornerstone.

“Therefore you are no longer strangers and foreigners, but fellow citizens with the saints and members of God’s household, built on the foundation of the apostles and prophets, with Christ Jesus Himself as the cornerstone.”— Ephesians 2:19-20 (BSB)