Tonea Stewart was blessed enough to be the recipient of intense training and mentorship from theater legend and the father of "Being", Frank Silvera. While actress Beah Richards was his first student, Tonea was his last.
In 1952, Silvera made his film debut in the Western The Cimarron Kid. Due to his light complexion, he was cast in a wide variety of ethnic roles in films and television.Later that same year, he was cast as Mexican General Victoriano Huerta in Viva Zapata!, starring Marlon Brando. The role marked the first time a major motion picture studio cast a non-white actor in the role of a non-white character. Silvera also portrayed the role in the stage production which opened at the Regent Theatre in New York on February 28, 1952. He appeared in two films directed by Stanley Kubrick, Fear and Desire (1953) and Killer's Kiss (1955). In August 1955, he appeared on Broadway with Helen Hayes in the revival of Thornton Wilder's The Skin of Our Teeth, which earned him favorable reviews. In November 1955, Silvera played John Pope, Sr., the Italian father of Ben Gazzara and Anthony Franciosa's characters on Broadway in Michael V. Gazzo's A Hatful of Rain (a role portrayed by Lloyd Nolan on screen). His performance was also praised by critics.
Silvera was also active in television. He made guest appearances in numerous television series, mainly dramas and Westerns, including Studio One in Hollywood, Alfred Hitchcock Presents, Bat Masterson, Thriller, Riverboat, The Untouchables and Bonanza. In 1962, he portrayed the role of Dr. Koslenko in The Twilight Zone episode "Person or Persons Unknown", opposite Richard Long. That same year, he played Minarii, a Polynesian man in the 1962 film Mutiny on the Bounty, starring Marlon Brando. In 1963, Silvera was nominated for a Tony Award for Best Actor in a Play for his performance as Monsieur Duval in The Lady of the Camellias.
In 1964, Silvera and Vantile Whitfield founded The Theatre of Being, a Los Angeles-based theater dedicated to providing black actors with non-stereotypical roles. One of the theater's first projects was the production of The Amen Corner by the African-American writer James Baldwin. Silvera and Whitfield financed the play with their own money and donations from friends. It opened on March 4, 1964 and went on to gross $200,000 within a year. The play moved to Broadway in April 1965. The play's star, Bea Richards, won critical acclaim for her role.
For the remainder of the 1960s, Silvera continued his career in film and guest starring roles on television. In 1965, he appeared as the Biblical Magi Caspar in the epic film The Greatest Story Ever Told, In 1966, re-teamed with Marlon Brando for a third time in the Western The Appaloosa. The following year, he portrayed Nick Sorello in The St. Valentine's Day Massacre, followed by guest roles on Dundee and the Culhane and The Wild Wild West. He also appeared as a Mexican bandit in the 1967 Martin Ritt Western classic, Hombre, based on the Elmore Leonard novel. In 1969, Silvera had a supporting role as Goatherd in Che!, and as Lobero in the Zapata Western Guns of the Magnificent Seven.
At the time of his death, he had a recurring role on the NBC western series The High Chaparral as the Mexican squire, Don Sebastian Montoya. Silvera's final film, Valdez Is Coming, was released posthumously in 1971.