I see no reason to doubt that it is a Lewisia.

I agree with Floral.

It is probably one of the modern hybrids and not a species.

For nerds: the current thinking is the whole lot are now Cistanthe.

It is a Lewisia, one of the hybrids with quite a bit of cotyledon in it.

"This genus is accepted": Lewisia Pursh | Plants of the World Online | Kew Science

"The number and circumscription of species in Lewisia are not widely agreed upon because of morphological variability and intergradation": Lewisia in Flora of North America @ efloras.org

Notice that in both treatments Cistanthe is not even listed as being a synonym of Lewisia.

Given the variety of leaf structures, is there an online taxonomy of Lewisia that would show the main variations?

There are individual descriptions linked to the key to species in the efloras online account. But: is there a species or cultivar name on the nursery tag?

@Embothrium I bought this plant on etsy and there is poor attention to detail on species/varieties.

Mixed colored garden strains of Lewisia cotyledon are prevalent on the market; that species is what your plant looks like. With certain other kinds that have become frequently seen in garden centers producing a different-looking plant. The main thing with L. cotyledon is keeping it from being rained on much. Yet not desert dry around the roots.

@Embothrium I have developed my own variant of the gritty mix for raised beds that seems to have a "just-right" level of water retention for succulents. The Lewisia just pop right to life in that soil. It was all about playing with particle sizes to get the adhesion level for water below the surface to be the right saturation level.

@Embothrium The efloras page has no photos, and I am really looking for a pictorial guide to the genus.

The particular issue with Lewisia cotyledon is rotting off of the crowns at the neck when there is a lot of rainfall. So that the texture of the soil beneath the level of the crown is not particularly relevant to this specific aspect of trying to keep them going.

@Embothrium That might argue for putting the top of the crown above soil level and maybe mulching with some gravel?

Fun fact: I just read that Lewisia gets its name from Meriwether Lewis, who discovered it during the Lewis & Clark Expedition of the West, in early US history.