Could you replace sour cream with ricotta and not ruin it?

Hi! If it's whole-milk ricotta, I imagine that would work just fine. There are also lots of great cake recipes that use ricotta to begin with—like this one https://food52.com/recipes/10436-louisa-s-cake or this one https://food52.com/recipes/77868-ricotta-rosemary-cake-with-fresh-figs. Hope that helps!