"Yes sir, Mr. El Moussa," the body art reads.
Heather captioned the shot, "Happy Valentine's Day Mr. El Moussa [heart and diamond-ring emojis] @therealtarekelmoussa I love you handsome! Best Friends Forever." She added a number of hashtags, including #tattoo and #soulmates.
E! News has reached out for more details on the tattoo.
Tarek commented on it with, "Forever and ever and ever," followed by six heart emojis. Heather responded back with four hearts, a heart-eyes emoji and the words, "love you so much."
Reality TV personality Lindsie Chrisley Campbell commented, "This is a vibe [fire emoji]." Heather replied with a heart emoji.
The photo also included a close look at the recently upgraded band on her 8-carat engagement ring that Heather debuted on her Instagram Story last week. She revealed at the time that Tarek purchased it for her after the pair had designed her ideal band together.
The couple got engaged on July 25, 2020 during a boat trip to Catalina Island off the coast of Southern California. Last month, the 39-year-old Flip or Flop star, who shares 10-year-old Taylor and 5-year-old Brayden with ex-wife Christina Anstead, posted a message to Instagram that offered details about the start of his whirlwind romance with Heather.
In October, Heather revealed that the pair had picked a date and location for their planned nuptials. She didn't offer further details, although she posted earlier this month that the wedding is set to happen in 2021.
Heather and Tarek first spurred romance rumors in July 2019, roughly three years after he and Flip or Flop co-star Christina shared that they were divorcing.