It is a major chord. Actually, tonic is simply defined as the first note in the scale or key. All chords have tonic note. The tonic of a C chord is the C. The tonic of a C minor chord is a C. The tonic of a C minor major 7 is a C.
Ascending up the major scale, the terms for each degree are the tonic, supertonic, mediant, subdominant, dominant, submediant, leading tone, and tonic again. The prefix "super" means above the tonic, and "sub" is below the tonic.