The answer is Caesar. What is the question?

VNUGPEUISLOGTDTQPEGEXUCTSPGHEUDUK?

Your task is to decode the message.
First you need to find the cipher alphabet.
Then you must locate the shift key.
Fill the missing letters in the grid below.
Make words of length 6 in each row.

N   O   T   R   _   A   N   T   W
H   O   N   C   _   O   T   H   A
T   Y   E   N   _   U   L   F   O
U   H   S   A   _   A   R   I   A
V   E   W   E   _   S   I   G   N
I   S   L   I   _   U   I   D   E
L   Y   P   E   _   E   M   P   T
R   O   D   T   _   I   T   C   H
T   W   E   E   _   E   U   C   E
D   A   E   M   _   A   R   K   L
L   O   R   E   _   O   K   E   F
T   H   E   S   _   R   U   P   Y
W   A   T   O   _   I   C   O   R
R   O   C   O   _   O   D   S   L
O   O   K   E   _   E   V   E   N
T   O   R   E   _   O   I   N   T
H   E   X   C   _   T   E   E   I
R   D   Y   A   _   I   C   O   U
T   E   H   A   _   L   O   T   R
E   X   E   M   _   T   L   E   T
T   E   R   A   _   I   S   H   R
S   F   R   U   _   T   L   E   O
R   T   I   R   _   N   E   D   H
E   N   E   N   _   V   A   H   O
G   A   D   G   _   T   X   T   S
T   S   T   A   _   U   S   E   P


The question is:

What is a cryptologist's favorite salad?

The filled in words is as follows:

N   O  (T   R   U   A   N   T)  W
(H  O   N   C   H   O)  T   H   A
T   Y  (E   N   G   U   L   F)  O
U   H  (S   A   F   A   R   I)  A
V   E   W  (E   N   S   I   G   N)
I   S  (L   I   Q   U   I   D)  E
L   Y   P  (E   X   E   M   P   T)
R   O   D  (T   W   I   T   C   H)
(T  W   E   E   Z   E)  U   C   E
D   A  (E   M   B   A   R   K)  L
L   O  (R   E   V   O   K   E)  F
T   H   E  (S   Y   R   U   P   Y)
W  (A   T   O   M   I   C)  O   R
(R  O   C   O   C   O)  D   S   L
O   O   K  (E   L   E   V   E   N)
T   O  (R   E   J   O   I   N)  T
H  (E   X   C   I   T   E)  E   I
R  (D   Y   A   D   I   C)  O   U
T   E  (H   A   R   L   O   T)  R
(E  X   E   M   P   T)  L   E   T
T   E  (R   A   K   I   S   H)  R
S   F  (R   U   S   T   L   E)  O
R   T  (I   R   O   N   E   D)  H
E   N   E  (N   A   V   A   H   O)
(G  A   D   G   E   T)  X   T   S
T  (S   T   A   T   U   S)  E   P

Which gives us:

The cipher alphabet: UHGFNQXWZBVYMCLJIDRPKSOAET. Observe that the unused letters in the grid spell out "Now that you have wisely produced all of the words, look to their outer letters for the next step"

Reading the outer letters of each 6 letter word gives the following:

"These letters are red herrings" for the first letter of each 6-letter word and
"To find the key, connect the dots" for the last letter of each 6-letter word.

The next step is to:

Connect the dots in the first paragraph of text to give the following:
Which tells us to shift the letters in the original phrase by 3 using the cipher alphabet we found.

Finally:

Doing exactly that on the phrase "VNUGPEUISLOGTDTQPEGEXUCTSPGHEUDUK?" given at the top gives us the question "What is a cryptologist's favorite salad?", which has the answer "Caesar".