What does that even mean?

lisaviolet thought this was worth mentioning said

Over in Twitterville someone posted a link to a news story about someone annoyed that a landlord doesn’t want her renting because she has firearms.

I didn’t read the story, but I didn’t need to. I responded “My house, my rules”. Landlords have all sorts of rules, like no pets, no children, no smokers, on and on. As long as it’s not legal discrimination, I don’t see a problem with it.

So, someone responds to me “My cake, my rules. See how that works?”

What the hell does that even mean?