In a large skillet on medium-high heat, heat oil and add the next 3 ingredients (onion though asparagus) and cook until all have softened slightly, about 10 minutes.
In a medium-size bowl, whisk together the next 3 ingredients (eggs through salt and pepper) and add to heated skillet with vegetable mixture. Lay tomatoes slices on top of skillet. Bake for about 30 minutes, or until the eggs have set. Serve warm.