Clean your portobello mushrooms with a damp paper towel or kitchen towel.
Cut the edges of the mushrooms and remove the inner stem to make a hollow circle inside the mushrooms to stuff them. Chop all the excess mushrooms and set aside to add to the stuffing mixture coming up.
Place the hollowed-out mushrooms on a cutting board or sheet tray and drizzle them on both sides liberally with extra virgin olive oil.
Toss the mushrooms on both sides with some garlic, thyme, salt, and pepper.
Grill mushrooms on high heat to sear them until they’re ¾ cooked and set aside.
Meanwhile in a medium pan on medium heat, add extra virgin olive oil to the pan, and then add chopped onion. Cook the onions halfway and then add the reserved chopped mushrooms to the pan. Then add the rest of your garlic, some more fresh thyme, oregano, salt, and pepper to the mixture, and cook until mushrooms are soft.
Add the spinach to the pan little by little until completely cooked. Season with a bit more salt and pepper.
Turn the heat on low and add the fresh tomatoes and lime juice to the pan. Season again with a little more salt and pepper.
Turn off the heat, and begin to stuff the mushrooms with this mixture.
Top the mushrooms with crumbled feta and bake in a 375 degree oven for 6-8 minutes or until mushrooms are tender and juicy.
Top mushrooms with a little extra juice from the bottom of the pan and enjoy this nourishing tangy delightful Mediterranean stuffed mushroom!