California Code, Government Code - GOV § 65356

(a) The legislative body shall adopt or amend a general plan by resolution, which resolution shall be adopted by the affirmative vote of not less than a majority of the total membership of the legislative body. The legislative body may approve, modify, or disapprove the recommendation of the planning commission, if any. However, any substantial modification proposed by the legislative body not previously considered by the commission during its hearings, shall first be referred to the planning commission for its recommendation. The failure of the commission to report within 45 calendar days after the reference, or within the time set by the legislative body, shall be deemed a recommendation for approval.

(b) A general plan of a charter city shall be adopted by resolution of the legislative body of the city, or the planning commission if the charter so provides.