One Pan Chicken Burrito Bowl

Name: One Pan Chicken Burrito Bowl
Ingredients: 1 lb Chicken Breast ((Boneless, Skinless)); 1 small Onion; 3 tbsp Olive Oil ((Divided)); 1 cup White Rice ((Uncooked)); 14.5 oz Diced Tomatoes ((1 Can, Undrained)); 15 oz Black Beans ((1 Can, Drained and Rinsed)); 1/2 tsp Garlic Powder; 1/2 tsp Chili Powder; 1 tsp Cumin; 3 tsp Chicken Base/Bouillon; 2 1/2 cups Water; 2 cups Grated Cheese (Cheddar, Colby Jack, or Pepperjack) ((8 oz)); 1 tsp Salt ((Plus More to Taste)); 1/2 tsp Pepper ((Plus More to Taste)); 2 small Roma Tomatoes ((Diced)); 1 medium Avocado ((Diced)); 1/2 cup Cilantro ((Diced)); 3 sprigs Green Onion ((Diced)); 1/2 cup Sour Cream