Preheat the oven to 360°F (182°C). Lightly grease a 9×13-inch casserole dish.
Spread the uncooked basmati rice evenly across the bottom of the prepared baking dish.
Add the finely chopped onion and minced garlic.
Pour the chicken broth over the rice mixture and gently stir to combine, keeping the rice evenly distributed across the bottom.
Add the cubed chicken breasts, black beans, drained corn, and salsa.
Sprinkle the chili powder, paprika, and black pepper evenly over the ingredients.
Stir the upper ingredients gently to distribute the seasonings while keeping as much rice as possible submerged near the bottom of the dish. This helps the rice absorb the cooking liquid properly.
Level the ingredients into an even layer.
Sprinkle the shredded cheddar evenly over the casserole.
Cover the baking dish tightly with aluminum foil.
Bake the High Protein Southwest Chicken Casserole for approximately 45 minutes.
Carefully remove the foil and check the rice. It should be tender and the chicken should be nearly or completely cooked.
Return the casserole to the oven uncovered and bake for approximately 10 more minutes, until the cheese is melted and bubbling.
Check the chicken with an instant-read thermometer. The thickest pieces should reach at least 165°F (74°C).
Remove the casserole from the oven and allow it to rest for 5–10 minutes before serving.