Seeing that houses and rooms in houses usually represent our hearts (in some cases it represents churches or congregations), I do think that this dream is probably about a certain aspect in you or about you. It is as if you forgot about an aspect of yourself. The kitchen represents a place where spiritual food is prepared (teachings, the word of God, and of course the fruit of the Spirit). The watermelon is a fruit and therefore it represents the fruit of the Spirit. It is very big which speaks of this divine fruit in your heart, big and/or strong. The sweet taste speaks of this divine fruit in you being very pleasant to people around you who “eat” it. So this aspect in your heart that flows out of you into people that you have contact with, is pleasant and wonderful to experience.
There is a possibility that this house does represent an old or previous church or congregation that you left for a time. You discovered it again and you are impressed with the divine and pleasant experience in this church or congregation. The same qualities about the fruit of the Spirit that I mentioned about you can be applied to this congregation.
Whatever it represents, the trigger that caused this dream will help you to understand the meaning a lot better.