What is a similarity between followers of Judaism and Christianity?

Both have a monotheistic outlook. (The belief that there is only One overseer of the earth's fate and those who inhabit it.)

Traditionally, both Judaism and Christianity believe in the God of Abraham, Isaac and Jacob, for Jews the God of the Tanakh, for Christians the God of the Old Testament, the creator of the universe ... Both religions agree that God shares both transcendent and immanent qualities.