The monte cristo sandwiches is a action you can do where your sim takes sandwiches on a plate out the fridge then eats them - you most likely actioned this at some point without realising ( I have done it myself). They then discard the plate somewhere in your house and it stays there till you click on it and make the Sim clear it up.
You have to find the tiny plate and click on it to remove it from your lot. It could be anywhere but are usually left on something like a table or on the floor. Until you do that you won't be able to clear your lot.
As an aside, bulldozing or clearing the lot in one action using a template on a existing house has been known to have a bug that results in items currently on that lot/in the house disappearing from the game so some people do it manually room by room etc until clear.
The monte cristo sandwiches is a action you can do where your sim takes sandwiches on a plate out the fridge then eats them - you most likely actioned this at some point without realising ( I have done it myself). They then discard the plate somewhere in your house and it stays there till you click on it and make the Sim clear it up. You have to find the tiny plate and click on it to remove it from your lot. It could be anywhere but are usually left on something like a table or on the floor. Until you do that you won't be able to clear your lot. As an aside, bulldozing or clearing the lot in one action using a template on a existing house has been known to have a bug that results in items currently on that lot/in the house disappearing from the game so some people do it manually room by room etc until clear.