Preheat oven to 180C/Gas 4.
1) Heat the olive oil in a small skillet over medium-high heat, add the onions and garlic and cook stirring occasionally until soft and brown, about 8 minutes. Transfer to a food processor, along with the spinach, potato, milk, egg, egg white, Worcestershire, lemon zest, mint, cloves, salt and pepper. Pulse until everything is finely chopped and evenly mixed together.
2) Use a rubber spatula to transfer spinach mixture to a bowl. Add the turkey, and stir everything together. Transfer meatloaf mixture to a 23 by 8cm loaf pan and bake 1 hour and 15 minutes. Remove loaf from oven, let rest for 5 minutes.
3) Chop the tomatoes and toss with the olive oil, salt and parsley. Slice meatloaf and serve with the tomato salad.