Instructions

1. To prep the tomatoes, cut the tops off. With a paring knife, cut out the middle, then scoop the flesh and seeds out with a spoon. Lightly salt the inside of the tomatoes and place them on a plate upside down (this helps to get rid of excess water).
2. 
3. In a large skillet, heat 1 1/2 Tbsp of olive oil over medium-high heat. Add the mushrooms and cook stirring occasionally until the mushroom liquid has evaporated.
4. Push the mushrooms to one side of the skillet. Add 1/2 Tbsp olive oil and the onions to the other side of the skillet and cook the onions stirring occasionally until the onions are translucent. Keep an eye on the mushrooms too. Add the garlic to the onions and cook for another 30 seconds then mix the onions, garlic, and mushrooms. ( Alternatively, you can also cook the onions and garlic first, set them aside and then cook the mushrooms. I prefer to cook them together to save time).
5. Once the mushrooms start to brown, add the spinach and cook, stirring constantly, until the spinach is wilted.
6. Add the feta cheese and cook until feta starts to melt.
7. Preheat the oven to 400F.
8. Using a spoon, stuff the mushroom mixture into the tomatoes. Place the tomato tops on top of the tomatoes.
9. Place the tomatoes in a baking dish. If the tomatoes have round bottoms, you can also bake them in ramekins.
10. Place the baking dish or ramekins into the oven and bake the tomatoes for about 15 minutes or until the tomatoes are soft. Do not overbake as the tomatoes will collapse if they are too soft.