Prepare toppings: In a large bowl, combine onions, jicama, corn and 2 tbsp lime juice. Season with salt and pepper. In a second large bowl, toss cabbage with 4 tsp lime juice and season with salt. In a third medium bowl, mash avocado to a chunky consistency; mix in cilantro and remaining 2 tsp lime juice.
Divide avocado, jicama mixture, cabbage and lobster among tortillas.
Avocado is the star ingredient of these tacos. Just substitute avocados for taco shells for the perfect low-carb taco. Load with ground beef, cheese, and a dollop of sour cream and you have a delicious lunch or dinner.