Preheat oven to 350°.
Heat olive oil in skillet. Add cut up steak and saute until cooked through. Salt and pepper. Set aside.
Mix bread cubes, cheese and 4 Tablespoons butter.
Spread bread mixture in greased casserole dish. Reserve 1½ cups for topping.
Top with peas.
Melt 6 Tbsps butter in skillet. Saute onions until tender.
Blend in flour and seasonings. Stir over medium heat, stirring, until mixture is bubbly.
Whisk in milk and heat to boiling, stirring constantly. Boil and stir 1 minute.
Stir meat into sauce and pour over bread layer in casserole dish.
Slice tomatoes and arrange over casserole. Sprinkle with remaining bread cubes.
Bake uncovered for 35 minutes.