Saute onion in butter until tender. In small bowl, beat together the eggs, half and half, milk, flour, and pepper until lightly frothy. Stir in the cooked onion, cheese, and toasted sliced almonds until well mixed. Pour the mixture into a still hot baked pie shell. Bake at 325 degrees F for about 45 minutes. When done, a knife inserted in the middle will come out clean. Let stand for 10 minutes, slice and serve.