In June 2015, after the release of her major-label debut, Kicker, Day started penning songs for her now unreleased third studio album.

"[4] "I Don't Know How to End", an album track, was reworked for Sunday in Heaven, although it was released to the public as a gift on her website in December 2018.

[11] Throughout that period, Day and Alex Casnoff co-wrote and produced "Radio Silence", and the title track was written and recorded.

[14] Paste's Candace McDuffle expands on her vocals by stating, "The captivating nature of Day's sultry voice can convince listeners of anything.

"[14] Prelude Press's Dom Virgil states that Sunday in Heaven is, "a record for moving forward out of darkness into light; for creating your own beautiful, sparkling reality exactly as you are.

The cover art was photographed by Elizaveta Porodina,[19] and features Day in a hot crimson, ripped, long-sleeved leotard, posed on an endless void of water, with a hot mixture of reds and oranges in the background, with the album's title and Day's initials in the upper right corner.

[24][25] The fourth single, "Radio Silence", was released on June 24, 2022, the same day the U.S. Supreme Court overturned Roe v. Wade.

[28] Prior to her tour announcement, Day marketed her album by performing at a variety of smaller venues across the US, and in appearing in interviews with independent music journalists.

AllMusic gave the record four out of five stars,[13] with reviewer Matt Collar expanding it by saying, "Singer Zella Day transforms into a glitter-laden, '70s-inspired pop diva on 2022's Sunday in Heaven."

"[13] Consequence's Joe Eckstein praised Day for her "spirit of freedom and liberation through her songwriting and impassioned vocal range, supported by genre-bending production", and elaborates that "Sunday in Heaven is a personal tale; one where snapshot moments of Day's life can be felt, the attention to detail in her lyrics forming vivid imagery.