Prepare the marinade by combining 1tbsp taco mix with the lemon juice and olive oil*. Pour over the chicken breasts and turn to coat, then cover and let marinate for about 30 minutes.  In the mean time, start cooking the rice according to the package instructions. When the rice has about 10 minutes left to cook, go ahead and throw the chicken on the grill. Remove the cooked rice from the heat and stir in the tomato sauce and remaining 2 tbsp of taco mix. Divide between two plates and go ahead and slice the avocado. If you care about the aesthetics of your food you won’t want to do that much earlier in the process or your slices will start to turn brown. It doesn't affect the taste but it won’t look as pretty.  Place the chicken on top of the rice and sprinkle the cheese over the chicken/rice. Top with avocado slices and generous dollops of sour cream.