In a food processor, combine all ingredients except steak. It’s usually best to add oil in a gentle stream while other ingredients are blending.
Once smooth, slather all sides of the steak in the pesto and place in crock cooker (adding any remaining pesto on top).
Cook on LOW for 6 to 8 hours or on HIGH for 3 to 5 hours, or until the steak is cooked tender.
Chop and serve in lettuce leaves as tacos or to top any summer salad.