Shaking Beef

Easy, awesome weeknight meal.  This is an adaption of a Slanted Door recipe that I found in Sunset magazine. 

1.5 lbs filet mignon, trimmed of excess fat and cut into 1" cubes
3 green onions, sliced
1 small yellow or red onion, thinly sliced
2 cloves garlic, minced
2 tbsp sugar
1 tsp salt
3 tsp pepper
4 tbsp sesame oil
4 tbsp white wine vinegar
4 tbsp soy sauce
1 tbsp butter
2 limes
Cover the beef cubes in sugar, salt and pepper.  Heat the sesame oil over high heat in a wok or heavy-bottom saucepan.  Once the oil is hot, add the beef cubes.  Brown the beef cubes for about 5 minutes. Add the butter along with the garlic and onions.  Saute for ~3 minutes. Add the vinegar, soy sauce and juice of the two limes.  Cook for an additional 5 minutes.  Serve over white rice.