On this video they explain the pronunciation of CAN-CAN'T, see if you can understand something and read the EXPLANATIONS box.

CAN /kn/         CAN'T /kan/

PRONUNCIATION

The pronunciation of this verb is peculiar, but it is very important to make the difference or they won't understand you.
---- affirmative
CAN /kn/
---- negative
CAN'T BrE /kaan/ or /kaant/    AmE /kan/ or /kant/
---- interrogative
CAN? /kn/ (or /kan/)

summary:
CAN /kn/         CAN'T /kan/
exception: at the end of a sentence CAN /kan/   CAN'T /kant/
e.g:  -Can you dance? - Yes, I can