Place all of the ingredients into a small food processor, blitz until it is a smooth consistency and set aside.
Add the sliced capsicums and red onions to a large mixing bowl.
Slice the chicken thighs into strips and add them to the bowl with the capsicums and onions. Drizzle over 2 tbsp olive oil, add the Mexican spice mix and toss well to evenly coat.
Heat a BBQ grill or a stovetop grill pan to medium-high heat. Add the capsicums and chicken allowing enough space to cook evenly, if you’re cooking on a small grill it’s best to cook in batches. Turn the capsicums once they start to blister and lightly char. Once the capsicums become soft, remove them from the grill and set them aside. Turn the chicken once light golden char marks develop, cook the other side then remove from the heat and set aside.
Toss the sliced tomatoes with the coriander leaves and a drizzle of olive oil, set aside.
To fill the fajita bowls first start by dividing the pre-cooked brown rice between 4 bowls, followed by the black beans, sliced tomatoes and the grilled chicken and grilled vegetables.
Slice the avocados in half, remove the seed and skin and thinly slice. Place one half into each bowl. Squeeze the lime over each avocado half to prevent browning.
Serve with a good dollop of the avocado sauce, extra coriander leaves and red chillies sprinkled over the top along with a wedge of lime.