Remember that on The Righteous Gemstones, Keefe was a Satanist before Kelvin brought him to Christ? Actually, it was more of a Goth/ fetish subculture that chanted "Hail Satan" for its shock value.
Here Tony finds a copy of Devil's Food: A Satanic Cookbook "in Keefe's storage unit." Good thinking: when you move in with a boyfriend, always keep the stuff from your old apartment, just in case.
It's a real book, written by Adam Ostrofsky (aka A Moveable Beast, har har), who runs a Satanism-infused catering company.
The Cavaleros don't mention spirituality much on their social media sites, but they are at least pagan-friendly. Here Annie promotes Grimoire Girl, by Hilarie Burton Morgan, "A meditation on finding as much meaning in the small moments as in the big, illuminating the enchantment and wonder and goodness in the everyday."