Heat the oil in a large skillet over medium-high heat.
Toss in the onion with a pinch of salt and sauté until the onions have softened, about 3 minutes.
Move the onions to the sides of the pan to create an open space in the middle. Add the cubed chicken into the center of the pan, season with salt and pepper, and sauté until the chicken has cooked almost all the way through.
Add the garlic and mix until fragrant, about 30 seconds.
Pour over salsa, black beans, and rice, and mix until everything in the pan is evenly combined.
Let the mixture simmer for 5 minutes or until the chicken is cooked through.
Divide the mixture equally into 4-6 bowls and sprinkle over some thinly sliced green onions.