Ingredients:

  Amount  Measure       Ingredient -- Preparation Method
--------  ------------  --------------------------------
2         tbsp          butter or margarine
1         small         onion, thinly sliced
1                       tomato, diced
2         tbsp          flour
1         cup           milk
1         tbsp          mustard
1/4       tsp           ground black pepper
2         cups          cubed cooked ham
2                       hard cooked eggs, sliced

Preparation:

Preheat the oven to 350 °F. Melt the butter in a 1-quart saucepan over medium heat. Add the onion and cook, uncovered, until soft, about 5 minutes. Reduce the heat to low. Blend in the flour and slowly add the milk. Cook, stirring constantly, until the sauce is thickened and smooth, about 3 minutes. Remove the pan from the heat and stir in the mustard and pepper. Pour half of the sauce into an ungreased 1-quart casserole; add a layer of half of the ham, all of the diced tomato, then a layer of half of the sliced eggs. Repeat the layers of ham and eggs, then pour the remaining sauce over all. Bake, uncovered, until the sauce is bubbly, about 20 minutes.