Why "gott"? Isn't "mat" an en-word?
It is, but gott is an adverb here, and adverbs are regularly formed like -t adjectives.
Oh, I understand. Tack så mycket!
so it is either gud or gott?
It has to be gott here because it's an adverb, not an adjective. It describes the verb tastes and therefore is an adverb; these are usually formed like the ett form of an adjective.