Season the chicken with the salt, pepper, paprika, garlic and onion powder. Heat a large skillet over medium heat and add the olive oil. Add the chicken and cook until browned and cooked through, flipping once or twice, about 6 to 8 minutes. Remove the chicken and place it in a bowl. Add the onion and brown sugar, stirring well to remove any brown bits from the pan. Cook, stirring occasionally for 5 minutes, or until golden brown. Stir in the pineapple and garlic. Cook for 5 to 6 minutes more, stirring often. Add the cashews and stir. Add the chicken back into the skillet and stir in the BBQ sauce. Let cook for another 5 minutes.