Black and Red Fiesta Beans with Rice

2 cups instant brown rice

1 (8-ounce) can tomato sauce

1/2 cup prepared salsa

1 tablespoon onion flakes

1 1/2 teaspoons ground cumin

1 teaspoon dried oregano

1 teaspoon dried thyme

1/2 teaspoon garlic powder

1/4 teaspoon cayenne pepper

1 (15-ounce) can black beans, rinsed and drained

1 (15-ounce) can white or red kidney beans, rinsed and drained

1 (11-ounce) can corn, drained

Salt and freshly ground black pepper