In large bowl or ziploc bag, add chicken, olive oil, orange juice, lime juice, garlic, and spices. Rub marinade all over chicken and place in fridge for at least 1 hour or up to 6 hours.
Remove chicken from marinade and discard marinade. Preheat grill to 425-450°F or a pan to medium-high heat. Cook for 5-6 minutes per side.
Transfer chicken to plate and cover with foil, letting rest for 5 minutes. Dice chicken into cubes.
Grill some tortillas for about 30 seconds per side until charred and set aside.
While chicken is resting, combine the chopped tomato, onion, cilantro, jalapeño, lime juice and sea salt in a bowl and set aside.
Serve chicken on warm tortillas with diced avocado, pico de gallo, and some cheese if desired.
Notes
Use chicken thighs: Yes I know thighs get a bad rap some time, but they have better flavor, get charred better and remain juicy even if you overcook.
Be patient when it comes to the marinade: You want to marinate the chicken for at least 1 hour, but I recommend trying to marinate for the full 6 hours so the chicken can absorb the flavor.
Hot grill: There is nothing worse than preparing chicken and then placing it on the grill and you don't hear a sizzle. You want the grill hot so you can get that nice char. It needs to be at least 425°F.
Let chicken rest: Yes even chicken should rest for a few minutes before you dice it up. If you chop into it immediately, the chicken will lose some of its juice.