I have found naturalization records for my husband's great aunt Regina (Handler) Solomon and her husband, Jake (or Jacob) Solomon. Because great uncle Jake Solomon finalized his citizenship in 1923, it doesn't look like Regina became a citizen at the same time because of changes in the naturalization laws.
The following documents can be found in "Naturalization Petition and Record Books for the US District Court for the Northern District of Ohio, Eastern Division, Cleveland, 1907-1946" at Fold3.
Note that at the signature line, the Deputy Clerk, Emil A. Bartunek, signed Jake Solomon and indicated that the "X" was his mark; Jake didn't sign his own name on this document.
Three and a half years later, Jake Solomon signs his name on his Petition for Naturalization, at the time, the second step to becoming a U.S. citizen.