Place the first 9 ingredients in a food processor with the chopping blade inserted. Process until everything is well combined; pour into a bowl and stir in the onion and tomatoes.
Season the steak with salt and pepper; grill. Slice the steak across the grain and toss with the tomato mixture. Arrange the lettuce on 3 serving plates and top with steak mixture. Sprinkle with cheese.
*I don't use the skirt steak, the butcher at my local market suggested using what they call "Sandwhich Steak" and it works out great.
I found this recipe on Linda's Low Carb Menus and Recipe's website. We love it.