Watch the C#7#9 online guitar lesson by Brad Carlton from Guitar Lab: Open String Universe
This chord voicing is achieved by moving the lowest four voices of the open E form up 9 frets. The first and second strings(voices) remain open and thus extend and/or alter the basic major chord which is always occuring in voices 6 through 3.
The voicing for this chord is as follows(from low to high in pitch):
6th string(voice) 1
5th string(voice) 5
4th string(voice) 1
3rd string(voice) 3
2nd string(voice) b7
1st string(voice) #2(b3#9)
Analyzing this chord against the 6th voice (as the root) reveals the name as C#7#9.
The applicable scale(s) for soloing over this chord would be:
C# half-whole diminished
1 b2 b3 3 #4 5 6 b7
C# D E E# F G# A# B