Steak and Baked-Tomato Eggs

3 T.olive oil
1/2 onion, thinly sliced
one 8-ounce pkg. white mushrooms, thinly sliced
salt & pepper
4 large tomatoes, tops sliced off and flesh scooped out (chop up for salad - see below)
4 eggs
1 T. chopped parsley
1# flank steak
juice of 1/2 lemon
watercress or other salad greens

1. Preheat oven to 375 degrees.
2. In a medium skillet, heat 2 T. oil, and then add onion and mushrooms. Cook until softened. Season with salt & pepper.
3. Fill tomatoes with mushroom mixture. Transfer to an 8-inch baking dish. Pack down the filling with a spoon and crack 1 egg on top of each. Season with salt & pepper. Bake until whites are opaque -- 20 - 25 minutes.
4. Meanwhile, preheat an oiled grill pan (or skillet) to medium high. Grill the steak, turning halfway through, for 12 - 14 minutes. Season with salt and pepper. Transfer to a cutting board and let rest 10 minutes before slicing thinly.
5. In a salad bowl, whisk together lemon juice and remaining T. olive oil. Add pepper then toss in greens. Top with chopped tomato flesh.
6. Serve salad with the steak and tomato-baked eggs.