Spinach Squares

1 stick of butter, butter
1 cup flour
1 cup milk
1 teaspoon salt or to taste
1 teaspoon baking powder
2 eggs, beaten
1 package frozen, defrosted and drained
1/4 cup chopped onion
14 ounces grated sharp cheddar cheese

Add flour, salt and baking powder to the melted butter. Mix and add milk, onions. spinach and cheese. Pour into 9x13 casserole dish and bake at 350 degrees for 25 minutes.