I don't know what you normally cook, but here's some suggestions based on my cooking habits. I value food that looks and/or tastes impressive, but is actually easy to prep and cook. I also stick to cooking things close to what I already know; I go out to restaurants to be adventurous.
Crock-pot chuck roast with potatoes, carrots, onion, and celery (veggies all diced). Salt, pepper, oregano, can of diced tomatoes, half can of water. Season and brown chuck roast in the morning in a cast-iron pan; place meat on bottom of crock pot, add water; veggies on top; season veggies; diced tomatoes on top of that. Set on low all day and it's ready when you're home from work. Makes a pseudo-stew. Just don't fill the crock-pot more than 3/4 or so full. You can also do this in a Dutch oven with a more abbreviated cooking time.
Oven roasted vegetables (seasonal). Roughly chop vegetables. Salt, pepper, olive oil, dried herbs (e.g. oregano, rosemary, sage). 400 degrees on aluminum foil-lined baking sheet until done (15-40 minutes depending on produce). Favorites: Brussels sprouts, butternut squash, asparagus, a mix of carrots/parsnips/potatoes.
Pan-fried white fish (Tilapia, etc.). Oil in pan over medium heat, Old Bay seasoning on fish. When fish is done (about 4 min a side), melt a tab or two of butter in the pan and add a handful of capers (drained) for about 30 seconds. Add a splash of lemon juice. Pour sauce over fish. Or skip the sauce and serve with a side of mayo mixed with Old Bay. Great with steamed veggies or a side salad.
Cast iron pan-seared scallops. Oil, salt, pepper, butter. Get them frozen at Costco or when they are on sale at your grocer. They take only 10 minutes or so to thaw. Do not crowd in pan; do not overcook! Serve with a side of quinoa and some arugula dressed with olive oil, lemon juice, and salt. Scallops are so easy to cook and so impressive. They are actually easier than most fish because of their uniform thickness, they are just too expensive for every day fare. But, they are cheap relative to comparable restaurant dishes. Alton Brown's Pork Wellington
. You can guestimate this, but I use a meat thermometer to make sure the pork's actually done. This is my favorite thing to cook to impress someone.
America's Test Kitchen Apple Pie (the cook book is worth buying). Sometimes I use store-bought dough (but not the pre-formed pie crusts with tin pans). It's almost as good, still looks homemade, and cuts the prep time down significantly.