Moreish is a word that you can use. This cake is very moreish. By indulgent, do you mean the food is bad for you? You can also use words like 'naughty' to describe food that is unhealthy but you like to eat.

You could use decadent or addictive.

You could say "it's very comforting". We talk about "comfort foods" in a similar way to "indulgent food(s)". This is food which is not necessarily the most healthy, but it makes you feel good and perhaps reminds you of the food you ate when you were younger. It is familiar and enjoyable to eat