It's 배우자 + 이다 in written/plain form, remain as in its dictionary form when gets added to a consonant, but when it gets added to a vowel 이 can be omitted.
배우자 + 이다 = 배우자이다 or 배우자다 - both acceptable.
빵 + 이다 = 빵이다.
You don't have to add 다, or anything else, because adjectives in the Written form in Present tense remain the same as in a dictionary.
이다 and 있다 also stay as they are.