"a confident command of" is correct and usable in written English.
It is typically used to describe someone's level of skill or mastery in a particular area. Example: She has a confident command of the English language, effortlessly expressing her ideas and opinions in a clear and concise manner.
The second painting, done in Rome a few years later, demonstrates a confident command of the basics as well as attention to Michelangelo's "Last Judgment" (especially in the figure of Jesus) and to Raphael's "School of Athens".
There were surprisingly smooth performances from the finance minister, Anwar ul-Haq Ahady, and the energy minister and former mujahedeen leader, Ismail Khan, who were expected to face strong criticism and questions about corruption, but showed a confident command of their portfolios.
It is rare for a young playwright to be in such confident command of all the theater's resources as Ms. Herzog is here.
She's in confident command of the stage, has a nice line in malapropisms ("I am very, very expertise on this subject") and – à la Les Dawson on the piano – her incompetent singing is the work of someone who knows which bum notes to hit and when.
She was in confident command of Prokofiev's florid, often vicious sieges of technical difficulty, and the nastiness lesser musicians bring to this music was softened to something almost moving, occupying a place somewhere between regret and resentment.
Despite his superb grasp of Russell's philosophical work and confident command of the details of Russell's private life, Monk, the author of a sympathetic yet rigorous biography of Ludwig Wittgenstein, is far too convinced of Russell's guilt to do his protean subject justice.
Brown proceeded to answer the reporters' questions with a display of self-confident humor and a command of facts, history and language that befits a man in the eighth decade of his life, as he likes to describe himself.
Use a strong, deep, and confident commanding voice.
Again, given that Mara was a fairly confident writer and wrote with a command of academic language, achieving such a dialogic paragraph may be considerably easier for her to do than the participants who struggled with academic language.
A confident state of intent emerges.
The more conservative Wall Street Journal is fulsome in its praise for Mitt: he appeared Presidential, "showed a superior command of fact and argument than the incumbent, and made a confident, optimistic case for change".
