Texas Barbecue Pot Roast

• 1 onion (sliced)
• 1/2 apricot preserves
• 2,000 gr eye of round bottom round
• 475 ml water for pork
• 350 ml water for beef
• 120 ml catsup
• 120 gr teriyaki
• 60 ml vinegar (white)
• 55 gr dark brown sugar
• 5 ml dry mustard