I can second Sally’s recipes.

We made this: https://sallysbakingaddiction.com/decorated-6-inch-cake/

It was really great! A perfect size for a family of 3.

Simply recipes super moist chocolate cake recipe. You can make it as a round cake or cupcakes, with or without the coffee
https://www.simplyrecipes.com/recipes/super_easy_super_moist_chocolate_cupcakes/

6 inch cake? Do you have a pan for that?
Just make cupcakes.

Can anyone recommend a simple 6 inch cake recipe (simple both in the making and the flavor) that I can make with my five year old? It’s for a birthday. Thank you!