Mexican Beef Salad

• 22 grams protein
• 20 grams fat
• 18 grams carbohydrates
• 1 onion
• 1,400 gr microwave-safe casserole
• 350 gr beef top round steak
• 100 gr torn lettuce
• 80 gr cherry tomatoes (halved)
• 45 ml vinegar
• 45 gr pitted ripe olives (sliced)