In a large bowl, combine the chicken cubes, olive oil, garlic powder, onion powder, smoked paprika, salt, black pepper, and cayenne pepper. Toss until the chicken is evenly coated. Cover and marinate in the refrigerator for at least 30 minutes, or up to 2 hours for more flavor.
While the chicken is marinating, prepare the chimichurri sauce. In a medium bowl, mix together the parsley, cilantro, garlic, red pepper flakes, olive oil, red wine vinegar, and salt and pepper to taste. Set aside.
Preheat the grill to medium-high heat. If using wooden skewers, soak them in water for 30 minutes to prevent burning.
Thread the marinated chicken onto the skewers, leaving a little space between each piece for even cooking.
Place the skewers on the grill and cook for 10-12 minutes, turning occasionally, until the chicken is cooked through and has nice grill marks. The internal temperature should reach 165°F.
Remove the skewers from the grill and let them rest for a few minutes. Serve with chimichurri sauce drizzled on top or on the side for dipping.