How To make Onion Tomato Cheese Pie

4 c Thinly sliced spring sweet
-onions (1 lb) 2 tb Margarine
1 Pie shell, baked (10")
2 tb Flour
2 1/2 c Shredded low-fat Swiss
-cheese 2 Firm tomatoes, sliced
1 cn Evaporated milk (5 oz)
2 Eggs
1 t Italian seasoning
Combine