Quick Quiche Lorraine

We have cooked this Quiche 3 times. It has been great each time. The last time we cooked it , we used Spinach instead of ham, we didn't do the tomato either. It was still great. I recommend this recipe. It cuts into 20 serves per dish, so it goes a long way too.
1kg diced ham
250 g finely chopped onion
50g butter
2 dozen eggs, beaten
360g all-purpose flour
2tsp salt
2lt milk
700g shredded cheddar cheese
sliced tomato to finish

Preheat oven to 175 degrees C. Lightly grease 2 mid-sized Bain Marie dishes.
Place ham and onion in a skillet with the butter. Cook over medium high heat until the ham is browned and the onions clear. Set aside to drain on paper towel.
Line bottom of the baking dishes with 3/4 of the cheese and all of the ham and onions. Combine eggs, salt, flour and milk; whisk together until smooth; slowly pour into baking dishes. Sprinkle the remaining cheese over the eggs. Gently place the slices of tomato so they are floating on top of the egg.
Bake for 1hour 15 minutes, until set. Check for doneness after 40 minutes. If the top is browning too quickly the oven temperature will need to be reduced to 160 degrees C.
Serve hot or cold. Serves 40