salmon-broccoli-brown rice casserole

Looking into my refrigerator, I see broccoli that needs to be used up.  I look at cupboards and see brown rice and canned salmon also needing to be used.  Plus, frozen onions.  So, some ideas from here.  I wanted to use sour cream instead of mayonnaise, but I am somehow out of sour cream.  I have no idea how that could be the situation in my refrigerator, and I keep staring in there as though it's tucked behind some sauerkraut or daikon.  It's not.  Aghast.  This time I used 1/2 mayo and 1/2 yogurt and it was fine.  I think it was a bit too rich so I've cut back the cheese to the recipe.  It is quite tasty though and will be used again.  

INGREDIENTS

1 cup chopped onion
1 tablespoon butter
3 cups chopped broccoli (fresh or frozen)
1-1/2 cups cooked brown rice
1 jar salmon, drained, skin removed (crush the bones - they're good calcium)
1 large egg, beaten
1/2 cup mayonnaise (or sour cream?  and/or yogurt?)
salt & pepper
1 cup grated sharp cheddar cheese (or less)

DIRECTIONS

In a large skillet, saute onion and then broccoli in butter until tender.

Remove from the heat; stir in rice and salmon. Combine egg and mayonnaise; stir into the salmon mixture.  Add salt and pepper.

Spoon half into a greased 2-qt. baking dish; sprinkle with 1/2 cup cheddar cheese. Top with the remaining salmon mixture. 

Bake, uncovered, at 350° for 30 minutes. Sprinkle with remaining cheddar cheese. Bake 5 minutes longer or until cheese is melted.