I would go with FAKE ROASTBEEF!!!
Easy & Fast, but looks like if you had been all the day in the kitchen...
* A roastbeef (the piece of meat of your choice, I do not know how to call meat pieces on English, but google says go with High tenderloin, I would call it "lomo alto")
* Onions, about 5 large onions would suffice
* Salt, white & black peeper, garlic
* Sweet wine (I love it with Porto's wine
, but my girlfriend prefers it with some Muscato wine
* A pressure cooker
* 45 minutes or so...
We will cook everything on the pressure cooker, so we reuse the same oil and clean less later
Pour some oil and quick fry the garlic. Remove the garlic and keep the oil warm.
Then you pour salt & peeper on the meat (as much as you like) and sear the meat with the oil (do not cook it, seal/sear/brown the piece, it must be slightly cooked in the outside, but totally raw on the inside).
Remove the meat and, add the onions (cut it in cubes) and let it cook. When it becomes brown, add the meat again, add the wine (about 1/2 - 3/4 liter, depends on what do you require for your cooker), some grains of white peeper and close it for the time your cooker requires.
When it finish, remove the meat and beat the liquid left (this would make the onion give more consistency to the sauce and remove big pieces) and it is ready.
Do not forget to hide the pressure cooker and put it in the oven before your guests arrive, so it will look like you did it on the oven!!