Believe it or not, roast beef is the perfect start to a speedy grab-and-go meal like this one by health and fitness expert Dai Manuel. Use a small beef oven roast (try a quick roast such as top sirloin, sirloin tip or inside round), or use a grilling steak instead if you like.
Season roast all over and place in shallow roasting pan. Insert ovenproof thermometer into the centre of the roast.
Oven-sear by placing uncovered in preheated 450°F oven for 10 minutes. Reduce heat to 275°F. Cook until thermometer reads 145°F for medium-rare or 160°F for medium doneness.
Carve cooked roast into super thin slices, cutting across the grain.
Heat a vinaigrette dressing to simmering and toss with onion slices to coat. Refrigerate in dressing.
Assemble tortillas by layering sliced roast beef on warmed tortilla along with avocado slices, marinated onion and chopped tomato. Top with cilantro leaves and a dollop of sour cream (optional).
Tip: Beef Quick Roasts are roasts cut in a small size that cook in under an hour - they make the perfect-sized slices for the tortilla. They are roughly the size of a pork tenderloin, and can be cooked in the oven or on the barbecue by indirect heat.