The easiest thing I can think of is roast chicken with roast potatoes.
All you need to do is put the chicken in a pan and stick it into the oven (count about one hour of cooking for a standard size chicken). Then in the rack under the chicken you can put another pan with potatoes (I'd pick the very small baby potatoes, not sure what they're called in english, as you won't even need to cut them up or peel them - just wash them and stick them in the oven).
The potatoes take about 40min so put them 20min after the chicken.
And then if you feel adventurous you can make a sauce with cream, chives, salt, pepper and a bit of lemon juice. But that bit is optional, you'll be fine with just the chicken and potatoes.
The great thing about that dish is that there's basically no prep or actual cooking involved. All you need to do is buy the chicken and potatoes and stick them in the oven. And it looks good because a roast chicken is always a bit festive.
If you're not keen here is another recipe that's fairly easy :
Get store-bought pastry dough (the savoury kind)
Get some thick sour cream
Get some bacon bits
Get some onion
Get some eggs
Recipe : put bacon bits in pan with onion on a medium fire till cooked
Mix the cream with eggs, salt and pepper, toss in the bacon bits and onion.
Now all you need to do is put the pastry dough in a pie mold, then you can pour in the pie mix, then put in the oven at 175°C till the pie is firm.
Serve with greens and tomato salad. If you feel adventurous you can make a vinaigrette (mix vinegar, olive oil and mustard).
It looks elaborate and you can make it in advance so you just need to reheat it quickly on d-day.
Damn this thread is making me salivate !!