Brush some olive oil on the bottom of a baking dish.

Clean the mushroom caps. Use a spoon to remove the gills.

Brush the olive oil onto both sides of the mushrooms.

Season both sides of the mushrooms with salt & pepper.

Set aside.

Preheat the oven to 450 degrees.

In a pan on Medium High heat add the butter.

Once the butter is melted add the onions and saute for 30 seconds.

Then add the tomatoes and saute for about 1 to 2 minutes until the onions are translucent.

Throw in the spinach and saute the spinach for about a minute.

Once the spinach is wilted immediately turn off the heat .

Spoon the filling into the mushroom caps.

Add cooked bacon if desired.

Top the mushrooms with cheese.

Transfer the stufffed mushrooms over to the baking dish and place in the preheated oven.

Bake for 15 minutes at 450 degrees.

Turn the baking dish around and then bake at 500 degrees for 5 minutes.

Total baking time is 20 minutes.

Place under the broiler for 15-30 seconds to brown the cheese. .

Remove from the oven and enjoy !

Add salt & pepper to taste.

And add a few dashes of Tobasco sauce for some heat. (optional )