Both forms are correct. Flavor and flavour are both correct spellings, only one of them is the American English version and the second one is British English. There is a slight difference in pronunciation in ending accent, the American version is pronounced like /ˈfleɪ.vɚ/ and British like /ˈfleɪ.vər/. It is a common case where an American word ends with -or and its British equivalent has ending -our. When it comes to meanings, they overlap.

Correct spelling, explanation: form mostly used in American English.

Correct spelling, explanation: form common in British English.

Definition of flavor/flavour:
Noun: the taste of food, drink or taste in general;
This meat has an unusual flavor, what spices did you use?
My favourite flavour is sweet, but my husband prefers salty snacks.
Verb: to add a particular taste to something;
I have flavoured this soup with marjoram, it gives a tasty note.
You should flavor this curry with a specific mix of herbs and spices.