Melt the butter in a large skillet over medium high heat. Add the onions and, stirring often, saute for a few minutes- until they've become tender and translucent.
1 tbsp butter, 1 large onion
Add the ground beef and garlic. Brown the ground beef completely, drain, and return to the skillet.
1 lb ground beef, 2 tsp minced garlic
Turn the heat down to medium and spice the beef with salt, pepper, and oregano to taste.
salt
Stir in the rice, peas, tomato sauce, broth, and 1 cup of cheese. Let simmer for 3 minutes.
1 14 oz can of tomato sauce, 1 cup of rice, 1 cup chicken broth, 1 cup frozen peas
Transfer everything to a 9×13 baking dish and bake at 350 degrees for 15 minutes.
Meanwhile, combine the sour cream, or yogurt, with the remaining cup of cheese.
1 cup sour cream, 2 cups cheddar cheese
After 15 minutes, remove the casserole from the oven and spread the cream/cheese mixture evenly over top.
Return to the oven and bake for an additional 15 minutes.