According to the CIA world fact website, the ethnic breakdown of people in Russia was as follows in 2002: Russian: 79.8%, Tartar 3.8%, Ukrainian 2%, Bashkir 1.2%, Chuvash 1.1%, other or unspecified 12.1% (2002 census)
No, Tatars are the second largest ethnic group in Russia. Tatars are a Turkic ethnic group native to Tatarstan, a republic within Russia.