Zest the lime. Combine with sour cream, cilantro, cayenne and black pepper. Peel and halve avocado. Slice thinly and place in small bowl. Squeeze lime juice over avocado slices and toss gently to coat. Pour off lime juice into sour cream mixture and combine. Lay each wrap out flat; evenly distribute ingredients between each wrap in the following order: sour cream mixture, beef, onion, spinach and avocado; spread evenly across entire wrap. Roll each wrap and slice diagonally in half.
Recipe provided by Certified Angus Beef