Preheat oven to 375.
Slice off 1/2 inch of the stem end of the tomatoes and hollow out the inside.
Slice just a small section off of the bottom of the tomatoes so that they will sit flat on a baking sheet.
Sprinkle salt in the hollow portion of each tomato and place hollow side up on a baking sheet.
Place water and quinoa in a saucepan.
Bring to a boil; lower to a simmer, cover, and cook for 15 minutes.
Heat oil in a frying pan and add spinach.
Season with salt and pepper, and cook until just wilted.
Mix in the garlic and parsley, cook for a minute longer, and remove from stove.
Add cooked quinoa to spinach; mix well.
Taste for salt and pepper.
Evenly divide the filling among the tomatoes.
Cover with foil and bake for 20 minutes.
Remove foil, sprinkle tops with parmesan cheese and mozzarella cheese.
Bake for an additional 5 minutes, or until cheese is melted.