If a cake recipe uses yogurt and oil for its fat can it be replaced with butter?

Hi Sarah! I would be hesitant to make that swap myself—cake recipes are pretty specific/sensitive and you would likely end up with a different result than the author intended. Here's a lemon cake recipe that calls for butter (and is Genius-certified, too!): https://food52.com/recipes/80782-maida-heatter-s-lemon-buttermilk-cake. Hope that helps and happy baking!